tyre load rating vs pressure?

I bought one of those church-on-Sunday grandpa cars, and the tyres were 8 years old, and the spare had never been used. So looked up what tyres I needed to buy. The tyre placard lists several options. Curiously, if 92 load rating tyre is used, minimum pressure is 29 PSI, but if 95 load rating, minimum pressure is only 26 PSI.
BTW since the car was made, it looks like load ratings have crept up. Nearly everything in my size is 99 load rating, only a few in 95.