Rank Vs Time

Time doesn't mean anything as you said you have afk hours. Other than that it depends because you could try compare yourself to another however it all depends where those 8k hours all on competitive or casual maybe surf? or other gamemodes that don't help you improve aim. Once you've learnt the basic game knowledge got a good team and good communication time becomes very little factor. Some people reach Global within their first thousand hours some never reach it. At the current moment global is basically just a hack fest anyway.