Random Number 0-1 Always Outputs 1

For the random 0-1 block, I created a procedure that goes like: If random 0-1 = 0 then spawn gem, else spawn a different gem. I repeated this multiple times to create a bunch of different chances, but I only ever get one outcome, even though I broke over 100 blocks. It only ever drops one thing, even though there's 20 different drops. The random 0-1 always comes out with 1, and never seems to come out with 0.

If anyone knows how to fix this, please let me know

Thanks!