The USGA says this about the "Second best score system":
The USGA has developed a simple estimator of a player's ability called "Second Best Score System" or "Second Best Handicap" for short. Second Best Handicap is not a substitute for the USGA Handicap System, but it can produce acceptable results and is a reasonable system for handicapping the otherwise "unhandicapped."
You can use this method to assign handicaps to players in League Manager. If you have scores from the previous season, it's preferable to use those scores to calculate an initial or starting handicap for the season.
Assign handicap using Second best score system
- Open Main Menu, click 1. Pre-Play and then click Manage.
- Click on player's name.
- Click on "Handicap #1" tab (see image below).
Click on "Instant handicap" button (see image above).
Input the second best score (see image below). If you are entering a 9-hole score, double it.
Click the Save button to assign and lock the handicap (locked handicaps show up in red print).