The number of strokes you are allowed in a round of golf is determined by the handicap provided by your club. An 18-handicapper will receive one shot on each hole, but a 28-handicapper will receive one shot on each hole but two shots on the ten most difficult holes as stated on the scorecard. Thus, a 28-handicapper can play anywhere from 14 to 20 rounds of golf per year. Players who carry a handicap of 9 or more are classified as "severely disabled" and are allowed only one swing per hole. They must use a different ball than normal players do. The ball used by severely disabled players is smaller in diameter than that used by other players and has a higher degree of spinability. Handicaps are calculated based on the number of strokes required for an average person to complete all eighteen holes of golf. For example, if an average person takes three shots to complete one hole, then his or her handicap would be 3. The number is reported to the USGA and assigned to every player before their first official tournament start. There are several methods used by clubs to assign levels to their members. Most systems rely on a percentage system where the player's score is compared to that of other players at his or her level. If his or her score is greater than 95% of those players, he or she qualifies for the next level up.