Why is the thermostat temp. range reading 30 degrees lower than it should be

Various ideas in the videos, but one of the articles said that Bertazzoni had a batch of bad thermostats. That model is discontinued/

https://www.google.com/search?q=bertazzoni+pro304inmxe+30+calibrate+oven+temperature

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no rule of thumb
maybe if you got a different thermostat that has a lower setting than standard
however as upright freezers are very bad freezers compared to chest type freezers the lowest reading will be around the -35 degrees C
Why very bad -- every time you open the door you dump 20 degrees out onto the floor and the temp difference is more pronounced than opening the lid of a chest unit which keeps all of the cold in the unit
remember the colder the setting the more the compressor is working

The range should be in the temp range of your thermostat within in a few degrees, you probably have a 190 degree thermostat. As the outside (ambient) temp rises it's normal for the engine to run a little hotter 200 degrees is safe with coolant, water boils at 212. Your fans should cycle, so it sounds like your temp sensor is faulty. if you haven't flushed your radiator and changed your thermostat lately, now would be a good time to do so. Hope this helps,

Is this oven gas or electric? If it is gas then it can be normal to see 30 to 50 degrees difference in tempature. The tempature in a gas oven works on the average tempature. For example: The oven tempature may rise all the way up to 370 degrees. Then the burner will shut off. And then the tempature can drop all the way to 330 degrees. Then take 330 and add that to 370 then divide that number by two and the average tempature will be 350. If your oven is electric then the tempature should be much more consistant but can have a 10 to 15 degree variance. Also the standard oven tempature guage that you put in the oven or even the temp guage built into the oven are not very accurate. We us a Fluke meter with a thermocouple to calibrate an oven. So to check your oven for proper tempature regulation you will first need to let the oven pre-heat for about 15 minutes. Then place the thermocouple in the center of the oven. If the oven is electric the take a temp reading every 5 minutes and average them out. If the oven is gas then you will need to take a temp reading when the tempature reaches it's highest and lowest points. Take at least 5 consectutive readings and average them out. You should get an average within 10 degrees of set temp(350 degrees). If it is off by 35 degrees or less you can usually caluibrate the thermostat back to proper temp. This procedure can be different for each range model. If it is more than 35 degrees off or you are getting irratic readings then the thermostat or thermostat components might need to be replaced.

this is most likely a bad thermostat

you shouldnt need to adjust the burners for a temp problem.
the control has a built in calibration setting and it should be described in your owners manual.
if you dont have the manual, then try to set the oven temp to max, 550, and then hold the bake button in for 10 to 30 seconds. after that it should beep and show you a 2 digit number like 00. that is the calibration mode, then you can adjust it up or down +/- 35 degrees. try to make a small adjustment first like 10 degrees and see how it bakes.
if it takes too long to bake, then use + degrees, if it is burning things then lower -10 degrees.
hope that helps you.

Obviously the thermostat calibration is out, most manufactures allow a tolerance of + or- 10%, so yours is outside this range.
You can compensate by setting the temperature lower by say 20 degrees, this will then bring it within accepted tolerances.
Hope this helps you.

195 degrees is the typical high end on the thermostat (when the thermostat opens), so the temp gauge should read a max of 195 degrees, give or take a few degrees. Some people replace their thermostat with a lower temp one, such as a 180 degree one. Then the gauge will read lower (approx 180 degree max). So the range is typically from cold at start to just under 200 degrees.

Hi if you look at temp gauge it is usually about 3/4 of the way up to the top any higher and this usually means thermostat gone or head gasket gone temp between 50 80 degrees depending on outside temp and how you drive diesel cars run a bit higher due to the amount of extra compression the pistons need to make the diesel flamable if you need further help let me know ok.
Also alot of newer cars run at temperatures lower than what i just said usually below half way but anyhing upto 3/4 of the way up is fine if it reaches the top this means engine problems or rad fan not working or thermostat not opening allowing the coolant to be pumped round engine properly as the thermostat opens when the water reaches a certain temp

If you oven temp is off by +- 50 degrees, thermostat needed to be change. to check and adjust the oven thermostat usually we place the oven thermometer in the center of the oven, run the oven at 350 degrees for minimum 30 minutes and check the oven temperature, It should be +- 25 degrees, if it needed adjusting, there is the adjusting slot screw in the center of the thermostat stem, to adjusting it ( do not turn thermostat stem during adjusting ), turn adjusting screw counter clockwise to raise the the temp, clockwise to lower the temp, turn it a little at a time and wait 15-30 minutes before do the next adjustment until the temp match with the oven knob. To adjust the oven burner air and gas mixture, first turn the air shutter close, you will see yellow flame, then open the shutter until the yellow flame disappear and them open it a little more, now you are done. For the oven uneven cooking? you may have a bad oven burner tube, during operation some of the flame may be lift off, disappear or flame being uneven, you can check it with the kick panels off to see the flame, if these are the case, you needed to change the oven burner tube,