Trading mode is explained in the user guide here
http://www.gruss-software.co.uk/Betting ... p/help.htm The user guide can also be viewed from the help menu within BA. You can read about it under "Betting Options".
Ideally I would like to remove it from the program because I don't think it is needed now. It' just that it was the only way of greening up in the first version of BA.
The basic difference is that when it is ticked it tracks the last bet you have placed and calculates the green up stake based only on that bet, it does not take into account bets on other selections. If you tick "Level profit based on individual selection" in grid preferences then the level profit will be based on all previous bets placed on the current selection the mouse is over. This is almost the same as trading mode except that it takes into account all bets on the current selection not just the last bet. This is more useful in my opinion.