I have done a handful of SF rentals lately and most are advertised in the MLS as paying $300-$500 commission . My question is I came across one in the MLS that advertised 10% referral fee. 10% of the whole lease? 10% of the 12 mnth gross?, thanks in advance

I would ask the source directly.

I don't know about SF, but in Manhattan, the typical commission paid to rental broker is 10%-15% of the whole year's lease, so it's possible that's what they mean.