It is supposed to mean "nearly" or "not quite", but alot of people would use it too mean "20+ mor minutes". in other words, "almost" can sometimes indicate a delay in a certain action.
"I'm almost finished cutting this man's hair, you're next!!"
20 minutes later:
"Dude, you told me 20 minutes earlier that you was almost done cutting this man's hair! WTF!!??!!!"
"sorry. I'm done now"
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