My pumps is set for 30 50 cut in and out. I put 28psi in pressure tank when pump hit 50psi. Should make air pressure still be 28psi? Or 50?

50. The 28# is where you should set the pressure with the pump off and pressure drained to zero by running water through a lower level faucet.

When you turn the pump back on, the pressure at the top of the tank will be about what you read on the pressure gauge.