Three sources of "correct PSI" (I use the term correct loosely).
The sidewall of the tire, as stated above is for carrying the maximum load (also on the sidewall)
The PSI on the GVWR sticker which is the correct PSI FOR THE OE TIRE if each axle is loaded to its GAWR.
The "real" correct PSI is to weight it and use your tire manufacturers inflation table to determine the correct minimum PSI (that is what the chart shows). Add 5-10 PSI to that minimum for those times all tanks are full, BIG shopping trip to Walmart, etc.