Math in bash is done with integers. It's not just rounding your decimals, there are no decimals. Dividing a number that is from 0 - 32767 by 32767 will give you 0 except for one case: 32767 / 32767. And, of course, 0 * 4 = 0.
What you want to do is multiply FIRST, divide LATER. So... intead of:
and that would give you a number between 0 and 3 inclusive, not between 1 and 4 inclusive.
The BEST way, by far, would be to use the modulus operator (%) rather than multiplying and dividing...
which will give you a number between 0 and 3 inclusive in one math operation instead of two.