This is probably a known issue, but the skeleton generator doesn't always generate a skeleton with the specified number of cards at each rarity (unless i've made some error)

Can you give specifics, please? What numbers did you fill in, what numbers were you expecting, what numbers did you get instead?

I don't remember off the top of my head, but I've had it give me 3 colored mythics instead of two, 5 common lands instead of 1, and 5 rare lands instead of 0. I've had other errors with colored uncommons, rare artifacts, etc