yeah i think you are border line over stocked, but it is quite simply cruel to keep just four neons. some people might a agree that frogs are fine but in my opinion and experiances they do eat fish. i would'nt always trust the lfs especially when they allow you to purchase only 4 neons. i would suggest at least 10 and a few more plants.
A lot of LFS advice can't be trusted, but I would say this makes them a bad one based on just that. I've gone in and bought 2 cardinals before to top up my shoal. The shopkeeper doesn't know whether the buyer is starting a new shoal or adding to an existing one.
I've found the same with my fish. Fish that look bright, glowing red in the shop are orange when I get them in my tank.