Falqon

I realize that this is a more complicated question than i'd like it to be, I don't know jack so there are probably lots of variables involved.

Assuming the pressure gauge is reading correctly, and assuming the engine is on and air conditioning is running full blast, is there a accepted number for the low side refridgerant reading? The reason I ask is I was curious if the recommended pressures that the generic wal-mart fill kits give are accurate.

Thanks for looking.