A few of things to be aware of while using Training Mode:
You cannot switch into training mode while you have active unmatched real bets.
You need to wait for the closed market report for your balance to be updated correctly.
Unmatched bets are cancelled when a market resumes after being suspended for 20 seconds or more. This is primarily to cater for football trading. This gives the user an experience that is virtually identical to real trading.
You can easily game the system, for instance placing large bets below (or lay above) the current trading price.
Money that you “take” in training mode will not be removed from the market, so you can repeatedly take the same money, which you could obviously not do in real money mode.