Hi guys, (But i think you don't are english), I have work on your code :
command /arenasetlobby:
permission: {@PermissionAdm}
trigger:
set {_num} to -1
open chest with 6 rows named "&6 SET ARENA LOBBY" to player # Here a changement because you make open the gui X times
loop 36 times: # I Have set "36 Times" because you have not defined the variable {arenas::*}
add 1 to {_num}
wait 2 tick
wait 4 tick
format slot {_num} of player with 1 carpet named "&a%{arenas::*}%" with lore "" to close then run [make player execute "/setarenawaitlobby"]
Sorry for my english but i'm french and it's a french forum, please, if you are english use a english forum like SkUnity etc.