Rune cap on pbe?

this isn't on my account that i've found this, but on my friends pbe account. I found that he has 30 of one rune, 27 of another, 9 of one. Having all these runes put him at being capped out on runes, but with all these runes and being rune capped. He can't own all the runes. I'm not sure how one would go about fixing this but it'd be awesome if you could thanks!