Normal operation. The rule of thumb is 10 psi per 1Krpm minimum. So, you are in good shape there. As you run the car, the oil gets hotter and the viscosity thins, hence lower pressures after a drive. You may find thay certain brand of filters/oils can produce higher/loweer pressures for any given situation. Personally, i prefer higher pressures (within reason) as it indicates plenty of oil flow in the whirly bits inside. The thing to watch for is a sudden change from what is "normal" for your car.