In simulated betting mode the BTX has to estimate when a bet would have been matched. It is impossible to do this 100% accurately as the BTX does not have access to the bet queue that is managed by the Betfair server and therefore does not know which or when bets have been placed and cancelled by other users.
At the point in time when a simulated bet is placed,the BTX will use the API to determine how much has already been traded at the required price or better. Then on each subsequent update cycle the BTX will check again and if the volume traded on the required price (or better) has increased then it will assume that this amount would have been matched on our bet.
