The exchange commission is a percentage of profit BetFair deducts from settled bets. The size of commission can vary not only across different users, but also across different sports and event markets within the same sport. It is always reasonable to account for the commission in any calculations you make when assessing a betting strategy.
To get the net amount of profit you will receive to your balance, you generally multiply your profit before commission by
(1 - commission/100).
For example, if BetFair applies the 5% commission rate to your winnings, then if you back £10 at 3.0, you will get £10*(3.0 -1) * (1 - 0.05) = £19.
Commission is always levied on profit, never on loss or zero winnings.
In MarketFeeder Pro you can choose for P/L to be displayed with or without the commission:
You can cancel an unmatched bet if a market is not suspended or finished. By cancelling your bet, you’re basically saying that you changed your mind and no longer want to back or lay on a selection. You can cancel multiple bets at the same time and immediately place new ones, with the same or different parameters.
See Green up.
A constant is a kind of user variable that is defined once and for all before the triggers start working. You can view constants are trigger settings, e.g. you can user a constant to define the size of bet or the minimum market volume.
We encourage using constants instead of plain numbers because it is much easier to control the values used by the triggers. If you need to change that value, you know exactly where to look for it – in the constants table, rather than checking every possible place where this value might be referred to.