jpascua wrote:

Can someone clarify what this means?

In Hard Mode, The computer takes enough tokens to make the size of the pile a power of 2-1 (1, 3, 7, 15, 31, or 63). 

What is meant by power of 2-1 (1, 3, 7, 15, 31, or 63)?

Thanks.

2, 4, 8, 16, 32, 64 are powers of 2: 2^1, 2^2 2^3...and so on... Subtract 1 from each result and you get 1, 3, 7, 15, 31, 63.

So, try taking 2 to the power of some whole number. That'd be 2, 4, 8, 16, 32, 64, and so on and so forth. Then subtract 1 from each of those numbers. That's where the list of 1, 3, 7, 15, 31, and 63 comes from.