In video, common frame rates are 30, 29.97, 24, and 23.976. (Almost) anything else will be a multiple of those. Your monitor might not actually run at 30hz * 4, it runs at 29.97hz * 4 which is why you see an option like 119.88. Sometimes that’s displayed as 120 to the user for simplicity, but in this case they’re showing the actual value (or it might support both).
In video, common frame rates are 30, 29.97, 24, and 23.976. (Almost) anything else will be a multiple of those. Your monitor might not actually run at 30hz * 4, it runs at 29.97hz * 4 which is why you see an option like 119.88. Sometimes that’s displayed as 120 to the user for simplicity, but in this case they’re showing the actual value (or it might support both).