Someone else might be a bit more familiar with LA, but I think that it is 4% - basically this means that if you sell to someone in LA, then you should charge 4%. I know this is the case in CA but the charge is more like 8.25%

As far as the amount you make I do not know. That seems about right but I bet someone else on here will have some more information on it. I doubt you have anything to worry about from last year though.