It'll exchange two Feoh runes for one sealed rune of the same level.
Maybe you will receive the rune that you wanted after releasing a seal. In the worst case you'll get the same rune as the one that you have given to me.
There's nothing bad in giving the runes that you don't need. Life is but a game.
Get one Lv. 1 Sealed Rune Get one Lv. 2 Sealed Rune Get one Lv. 3 Sealed Rune Get one Lv. 4 Sealed Rune Get one Lv. 5 Sealed Rune Get one Lv. 6 Sealed Rune Get one Lv. 7 Sealed Rune Get one Lv. 8 Sealed Rune Get one Lv. 9 Sealed Rune Get one Lv. 10 Sealed Rune Get one Lv. 11 Sealed Rune Get one Lv. 12 Sealed Rune Get one Lv. 13 Sealed Rune