dont get too hung up on perfection here... thats a rough estimate. you dont want to hydrate ALL the beads so that they are able to absorb humidity as well as release it.
the longer youre in the hobby, the less hung-up youll be on percentages
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"One fart can foul the air for everyone" - Esteemed philosopher
"If avoiding the nasty $hit is being a snob, them I am guilty as charged."- Same esteemed philosopher.