After 24 hours, provided the box has not been opened, you should have low side running pressure of 2-3 p.s.i.
Ordinarily, we weigh the charge prior to installing, since the exact amount is stamped on the model number sticker. This takes all the guess work out of it later, especially if you have a restriction somewhere that will distort the pressure readings. This may not be rocket science, but it is a science.
Charging Demo