OK, I understand the situation now,
-7.5 means the player will win
7 and a half "and since there is no half game" then will win by
8 games is a win and 7 is a loss (There is -7 where 7 is a tie and -8 where 8 is a tie)
+6.5 means the player will lose by
6 games at most and a loss with
7 games is a loss
There are the global spread rules, you can view them in any sportbook etc... just search it
The game between jennifer Brady v Maryna Zanevska ended 6-3 6-2 for jennifer (Therefore 3 and 4 = 7)
http://www.sofascore.com/brady-zanevska/DAqsyVvTherefore jennifer won by 7 games and lost the -7.5 and Maryna lost by 7 games therefore the +6.5 loses
if you wanted a tie, you needed the same value at both sides, it's the same but in seconds the spread changes in live betting, so even if you placed one and until it confirmed etc... the spread has moved and it became a one game higher/lower
Really tough loss though the only situation where both will lose...