[Poker Bookshelf]

You earn 1 point for each pot with $1 or more in rake, and 0.5 points for each pot that's raked $0.50. It takes 7 points to clear each bonus dollar.

Once reaon that it can take a while for small-stakes players is that does not collect any rake at all if the pot is less than $20 in $2-$4 and up. In $1-$2, the rake is $0.25 for eavery $5 in the pot up to $1.50 max. Below $1-$2. it's only $0.05 for every $1 in the pot up to $1.50 max.

So, ironically, this favorable rake structure does make it take longer to clear a bonus when playing very small stakes.