So I keep finding mixed answers from forums and ai on expansion tank psi

I'm trying to add an expansion tank to water heater on a 40 cut in 60 cut out well system. Check valve is fixing to be added right after water filtration system to keep it from backflowing everywhere. But I've got 38psi answers from ai which sounds like it's mixing up the bladder with expansion tank. I've also found 60psi 40psi and 50psi answers on forums. Even the qa for the expansion tank none of those answers are from a manufacturer only one i could find was for municipal water pressure which is a constant so I'm kinda Inna bind trying to figure out what the right answer is. Much appreciated and hopefully someone else will find this reddit question in the same situation as myself because the answers I'm finding are like Googling how many sticks of dynamite equal a gallon of gas. There's about 80 different numerical answers it's insane 🤣