Theoretically, those numbers should work.
From my experiences, I would count on the yields I have listed below - from a usable 17 x 20 area after washing (or a skimpy FQ)
80 - 2 inch squares (10 across x 8 high)
48 - 2.5 inch squares (8 across x 6 high) (If a usable 17.5 inches - 56 squares (8 across x 7 high)
30 - 3 inch squares (6 across x 5 high)
20 - 3.5 inch squares (5 across x 4 high) (If a usable 17.5 inches - 24 squares)
20 - 4 inch squares (5 across x 4 high)
12 - 4.5 inch squares (4 across x 3 high)
12 - 5 inch squares (4 across x 3 high)
9 - 5.5 inch squares (3 across x 3 high)
6 - 6 inch squares (3 across x 2 high)
6 - 6.5 inch squares (3 across x 2 high)
4 - 7 inch squares (2 across x 2 high) - (If fabric has 21 inch usable - 6 squares- 3 across x 2 high)
4 - 7.5 inch squares (2 across x 2 high)