About AWS RDS pricing

I have a question

I have a RDS : db.t2.micro with storage :20GB

It's now free tier usage. I want to know when the free period is over .

Is it priced by per hour??

I find this picture (http://aws.amazon.com/rds/previous-generation/?nc2=h_ls) is use hour to count the price .

will the storage(20GB) influence my bill?? Here didn't have info about db.t2.micro

I want to know this to decide whether I have to delete this RDS and open a new one just 5GB

Please guide me thanks!!