The old MSC that ran the PJ shops was very clear that you could not order extra food.
However, the MSC that has most of the ones now allows you to order extra food.
The guidelines encourage it in fact (I ordered a mega cookie on my last order and it was just fine).
The survey asks for the purchase amount for just the pizza and the purchase amount for the entire purchase.
If I ordered this deal with one pizza and one soda, I would just do a fake online order for a soda (and don't hit submit to truly order) to get the amount and just subtract it for the pizza amount.
Read the guidelines of the shop you have to see if this is the one you have. If you talk to a person on the phone (instead of self-assigning), they almost always add a bonus to the shop and I just use it for any extras I add.
Shopping across Indiana but mostly around Indianapolis.