Just got a reply from Tim on this for anyone else that was wondering:
Tim: Hi Paul
Tim: how can I help you?
Paul: hi, whats a High Roller Adjustment?
Tim: that relates to our ‘Highroller policy’ whereby under certain circumstances a negative balance is carried for a player
Tim: those circumstances are that a player’s balance for the month must be at least $10,000 and that your account at the casino they are playing at is in the negative by at least $2000
Tim: the negative balance is only ever carried against that particular player’s revenue and cannot affect revenue from any of your other players
Tim: it is basically a term which protects us from paying a big winner and then paying again if they lose the money back the next month
Paul: ok np Tim, just was wondering what it was because i have never noticed that before