trying to decide if I should bake more!

Do the math.

If you're going to cut them in the standard 2x2x2, then that means the cake will be cut in approx 4 rows by 6 columns = 24 servings.

If you're going to cut them larger, like 3x2x2, then that means the cake will be cut in approx 3 rows by 6 columns = 18 servings.

I tell my customers 24 servings but I rarely do sheetcakes anymore!

I tell my customers it serves 25..Thus I charge $2.00 per serving for slab cakes so cost would be $50.00

I've always said 18-20