An air-fork pressure chart is a starting point, not a finished setting for every rider. Riding position, equipment, bike geometry and terrain all affect how the fork behaves on the trail. The pressure marked for the fork gets the process underway; the final feel has to be judged while riding.
RockShox starts with the suggested pressure for the particular model. After inflation, the rider slowly compresses the fork several times to equalize its air chambers, then checks the pressure again. The reading may fall after equalization; that alone does not indicate a leak. The travel indicator ring can then be positioned before a ride.
A familiar trail makes changes easier to compare than one isolated impact. If the fork feels too harsh or uses its travel too readily, adjust gradually and follow the instructions for the exact model. Air pressure is only one part of setup; rebound and compression are easier to assess once the spring has a useful baseline.