Premier Bans

Asking for a friend but how long will a premier ban stand after getting an afk ban in normal queues?

Just for extra information he said he got banned for ~10 minutes and whenever I try to invite him it says I can't

2 months, weirdly enough, my computer was not loading in a 5 stack tdm to warm up(my teammates won) , and riot handed me a 2 months premier ban, when I asked for appeal they refused saying it’s not fair for everyone, like I don’t get what’s fair, premier penalty system is fkd like T2