A incorrect fax number got loaded into the memory by mistake. How do I delete it. It is a Pixma MX320 model

If you mean the fax number for your fax machine, you should be able to press the Fax button on the printer and then press the menu button, then go to settings. You should be able to change the original set-up information, including the fax number and other identifying features for your faxes.

If you mean for memory for other fax numbers, you should be able to to to the directory in the settings and edit or delete the memory settings much the same.