How many sauces are you entitled to with your McNuggets?

According to the McDonald's app you get 1 sauce with 4 McNuggets, 1 sauce with 6 McNuggets, 2 sauces with 10 McNuggets, and 3 sauces with 20 McNuggets.

If you get 1 sauce with 4 McNuggets it seems like you should get 5 sauces with 20 McNuggets! Or at lest 4 sauces because double the 2 with 10 McNuggets would be 4. Offering just 3 seems just wrong.

But at the local McDonald's they have a whole different formula on a posted sign (sign also does not properly capitalize "McNuggets"). They give 2 sauces with 6 McNuggets, 3 with 10 McNuggets, 5 with 20 McNuggets, and then 8 with 40 McNuggets. The 4 piece to 20 piece conversion makes more sense at the store. But then to go to 8 sauces with 40 pieces doesn't make sense again.