I've just been trying out some tennis trading in practice for Wimbledon and have observed what appear to be two separate markets between website and API.
For example in this match Tipsarevic v Seppi, the markets show as follows before start of match.
Website Total Matched = £23246
API Total Matched = £9463
Website Price Spread Tipsarevic : 1.33 - 1.34
API Price Spread Tipsarevic: 1.36 - 1.37
LOL, just worked it out - it's the final so there are two separate markets - one for the match itself and the other one that started before the tournament started and is now down to the last 2 players.