The total number of sets will be added or reduced from the final score of the sets in a tennis match.
For example:
Federer is playing against Djokovic
Set Handicap line for Federer: -1.5 sets
Set Handicap for Djokovic: +1.5 sets
Final result is 2-1
If you bet on Federer -1.5 sets you lose, if you bet on Djokovic +1.5 sets you win.