Keeps spilling over during brewing - Bunn VPR Coffee Maker

These tanks can't actually be overfilled since all water poured in displaces the exact same amount of water coming out the spout. So, whatever amount of water you pour in, will be the same amount of water that flows to your pot minus the amount absorbed by the coffee grounds and filter.

Your problems sounds like an undersized (Non Bunn) filter, or clogged brew basket. To verify this, try pouring in only half the water for your brew cycle and wait for it to finish dripping, then pour in the rest. If no overflow has occurred, you simply have the wrong type of filter. If overflow begins again, you have a clogged brew basket, since no Bunn can flow too fast for the brew basket to keep up with it.

This is because Bunn filters are manufactured differently than generic store bought paper filters. They will flow faster, brew cleaner and stand up better than normal generic filters.
Remember, Bunn makes their OWN filters for good reason.
They made the first, best paper filters for drip coffee pots, and all others are just generic dioxin gas producing paper.

With some of these machines it is possible to "overfill" the reservoir because, for whatever reason, the heating tank was not completely emptied to the correct level. When the tank is not properly emptied to that level and more water is poured in, all of what was poured in goes thru PLUS the excess water in the tank causing the pot to overflow. When this occurs, unplug the unit, completely empty it of all water and start again with the proper amounts of water. This should fix the problem.