Let's say you use a system when trading. That system might be as simple as 'When X happens, do Y', ie very precise and mathematical, no ambiguity.
Or a system could be discretionary, and just mean a set of approaches. If Betfair decide 'We are going to use less of Approach A and more of Approach B within our system', they could do so, and still claim that they are using the system they were previously using. As Betfair employ human traders, there presumably is a discretionary side to their trading, as otherwise you'd expect them to just use bots.
Jeff
PS I shall refer to you by your real name from now on, although people might start talking!

