Suppose a shot starts 125 yards from the hole and the end of the shot is 10 feet from the hole. Then the player’s average proximity from 100-150 yards is 10 feet. However, suppose the player’s shot started 150 yards from the hole. Then a shot to 10 feet from the hole from 150 yards is better than one starting from 125 yards, so the ending distance to the hole is scaled to reflect that difference. In particular, the proximity is reported as 10*125/150 = 8.3 feet. In this way, the proximity results a more consistent with each other when there is a limited amount of data.
In addition, proximity is computed as a median value, not an average. For example, suppose a player had three shots starting from 125 yards in the fairway. Shot 1 ended 10 feet from the hole, shot 2 ended 14 feet from the hole and shot 3 ended 100 feet from the hole. The median proximity of the three shots is 14 feet (the middle value of 10, 14 and 100). Using the median value gives a better measure of proximity than the average value because it is not heavily influenced by ‘outlier’ poor shots (in this case the shot that ended 100 feet from the hole).