Its not based on admin decision in that way. Its a random number so it isn't the same for all (throws off spammers) and it can change over time. A few means about 3 or so. It happens automatically based on number of posts "approved".
It becomes an admin decision that someone doesn't receive that functionality if they spam the forum... then i set the status so we all don't have to see the spam and eventually banned so I don't have to continually deal with that user spamming the forum.
Thanks for asking the question, I'm happy to explain whatever needed and I'm sure if you are asking others have wondered the same thing as well.