Counting

If we have a 4x4 grid and can place 1 counter in each square with 2 counters per square, we have that the each row can have 8 different arrangments for the counters. this applies to each of the 4 rows, so you hvae 8*8*8*8 possibilities, which is 4096.
If we are placing 3 counters in each square, we can have 4 possibilities for each row, which is 4^4 or 256 possibilities.
Very sorry I couldn't upload images, webcalc does not let me for some weird reason but I use mathigon to visualise this, so thanks to Melody for sharing it.
Hope This Helps!