I think I've got to say 1d6. Here's the thinking:
You narrated jumping down, not falling down. Neither is a defined term, so we should respect the distinction in English. (Jumping long and jumping high are detailed, but not jumping down.) So jumping down should be less injurious than falling down. Dropping a d6 is the simplest way to accomplish that.
I'll admit there's no rule that specifically says "jump = fall - 10'," but there's also no rule that says what falling even *is*. So we devolve to the explicit "deal with it yourself" rule.