Minus buttons represent undertricks.
The other buttons indicate how many tricks the declarer made [when he made the contract, possibly with overtricks].
You can ask the TD to change how the result of the play of the hand is reported if you find it awkward. The TD can change this anytime in the control programís settings.
HOW TO CORRECT MISTAKES
Mistakes should be corrected as soon as you spot them and at the very latest before the end of the round.
BridgeTabs offer several convenient methods to change incorrect entries, see a separate page for details.