Drug Possession: Can I Be Charged with a Tiny Piece of Marijuana in a Baggie

My question involves criminal law for the state of: Florida

On October 5, 2010, me and my brother and my friend we're coming back from school and we stopped at a gas station for a couple minutes cause we weren't ready to go home yet. So we were sitting there and then we were fixen to leave and my friend took his air freshners out and put them on the ground and the guy inside called the cops and said we were loitering and then we littered. So we were pulling out and getting on the road to go home and then we turned out and then when we turned out the cop was right behind us and pulled us over. They came up to the car, told us to get out and the cop started searching the car. Nothin was i the car but some lighters. Then he asked to search my bag and I said yeah go ahead, knowing I had a baggie in there. So he called me over and asked me how often do I smoke and I said not often and he asked when the last time I did and I said a couple days ago, which was why I still had the baggie in my bag. Now, there was a reaaally tiny piece of marijuana in it, smaller then a stem ( . pretty much the size of that dot) and he said he was gonna let the state attourny or something decide what to do so he took my information down and what not and we left. A month later I got a phone call from a probation place, I was on probation for a couple weeks and recently just got off cause now my mom wants to go to court for this cause she doesn't see why I'm being charged with marijuana when there wasn't really anything in the bag. I said the same thing. And it was my first offense of even getting in trouble with marijuana/paraphanelia. They should of never even put me on probation. So now I'm waiting to go to court for this and I don't think I should be charged except for the paraphanelia charge. What do you think? Also, isn't there a law that says you can't get charged with marijuana if it's less then 20 grams in the state of Florida?