GolfLeagueSite follows the USGA Handicap Formula
Within this formula, all scores do not affect your handicap.
For instance, the formula only counts your best ten scores out of your most recent twenty.
If you have fewer than twenty scores entered, then it has specific rules for which scores count based on how many scores have been entered.
In plain English, some of your really bad scores will not factor into your handicap.
For this reason your handicap may not increase after a really bad round but will likely decrease after a really good round.