This is how it works on my end.

Step 1
1 pile x 64 stones / 2 = 2 piles x 32 stones in each pile
Operations number on this step: 1

Step 2
2 piles x 32 stones / 2 = 4 piles x 16 stones in each pile
Operations number on this step: 2

Step 3
4 pile x 16 stones / 2 = 8 piles x 8 stones in each pile
Operations number on this step: 4

Step 4
8 pile x 8 stones / 2 = 16 piles x 4 stones in each pile
Operations number on this step: 8

Step 5
16 pile x 4 stones / 2 = 32 piles x 2 stones in each pile
Operations number on this step: 16

Total number of operations: 1 + 2 + 4 + 8 + 16 = 31

Hope this helps, good luck!