5% does seem a little high. I think Sam Altman called for a minimum of 10% (so the allocation is equal to x such that x us equal to or greater than 0.10) to go to the first ten hires. Perhaps, this would be a scenario where the first hire would get half of the allocation (so the allocation to the first employee is equal to x such that x is equal to or greater than 0.05).

However, I'd argue the first hire isn't "the least important junior assistant developer" no matter what label you put on them. Other than a first (or maybe second but that's stretching it) hire, I fail to see where someone would get five to ten percent.