A "Hard Cap" is triggered when a player has 20 scores in place and is a way of preventing their Handicap Index® from increasing too quickly, to ensure that a temporary loss of form does not cause a player’s Handicap Index to move too far from a level consistent with their demonstrated ability.
The hard cap triggers to restrict the amount by which a player’s Handicap Index can increase, after application of the soft cap, to no more than 5.0 strokes above their Low Handicap Index™
The soft cap and hard cap procedures start to take effect only after the Low Handicap Index has been established.
What is a Low Handicap Index:
Further details are available via the WHS™ Rules of Handicapping and can be downloaded at THIS LINK.