Yes Bostons.. this means -4.5 games in the match, is the pointspread or handicap in tennis.
Example:
Federer vs Roddick(Pick Federer -4) : 7-6;7-6;7-6: total : Roddick 18-21 Federer. Loss this wager. Federer won this match but in the games only won by 3 games. Roddick 18-17(21-4=17) Federer
Other:
Roddick vs Federer ( Pick Federer -4) : 7-6;7-6;0-6;0-6;7-6: total : Roddick 21-30 Federer: This match won Roddick but in the pointspread and our wager won Federer 21- 26(30-4)
Ihope that you understand this If dont I will answer all your question about this
. Sorry for my english