The setting that decides what happens when the price moves as you bet

Every account has a preference for what to do when the price changes between pressing the button and the bet being accepted: reject the bet, accept any better price only, or accept any change at all. The default is frequently the last of those, and it is the one that quietly takes a worse number on your behalf.

There is a real gap between your click and the operator's acceptance — network latency, a queue, a market being repriced — and something has to happen in it. Rejecting every change would fail a large share of bets during exactly the periods when markets move most, so the permissive default exists to make the product work. It is a trade of price for fill rate, and the trade is yours to set.

It does not mean the setting should always be 'reject'. On a fast-moving market a rejected bet often means no bet at all, and missing the bet you wanted is also a cost.

That is also the expensive part. The default is set once, at signup, by somebody who does not yet know what it does, and then never revisited. The bets it affects are individually too small to notice and collectively the size of a bad month.

What to do with it. Set it to accept better prices only, and see how often bets fail. If the failure rate is intolerable on the markets you actually bet, loosen it deliberately rather than by default.