Can someone tell when whats the extra room in the alt quelt mines which cant be accessed and what does the vouchers used for since ive collected from nearly all vouchers in alt quelt except for voucher number 8 and 13?

It says that i can get stuff from some stone at the entrance if i have 16 vouchers and i have more than that so how do i activate it for my prize?

-> Quest doesnt need to be activated, just kill the monster when he spawns and collect the voucher he drops from the different rooms (Correction to this, u need to talk to the stone in brown (NPC for this quest) at the entrance of the dungeon to activate it, esp for AQM. Not sure abt Tetra Ruins. Otherwise, the vouchers will overlap each other. I've tried it before.)
->AQM Dungeon has 22vouchers and Tetra has 16vouchers
->You cannot have more than one of the same vouchers at any one time
->Different number vouchers are acquired from different rooms
->After collecting all the vouchers, the reward can be claimed near the entrance area where there will be a "NPC" that looks like a statue
->The reward is randomly chosen from the list of items