As of the 1st of April 2024 changes have been made to the method used to calculate holes not started, using a combination of net par and expected score. This new method will produce a 9-hole or 18-hole Score Differential™ that more accurately reflects a player’s ability.
As golfers across the world are playing more 9-hole rounds, an expected score will also be used to convert a 9-hole round into an 18-hole Score Differential™. The calculations used to calculate an expected score, includes ratings of standard difficulty, and are not shared by the USGA. This means the Score Differential™ will more accurately reflect the playing ability of the individual golfer.
Note: If any holes are scored as "not attempted" the final adjusted score will be shown as a "*". This is because those hole/s will have an expected score calculated and applied to it/them. However, you will see a Score Differential for that round. For a score to be eligible for handicap purposes, a minimum of 9 rated holes must have been played over (either a Front, Back, or Composite 9).
Further details can be found by viewing THIS VIDEO.