Ok, so I've done a bit of investigation.
In time machine, it works as expected. tennis_player1_service_breaks is 0 until they score a break of serve, then it is equal to 1.
When running in betfair mode, I'm getting different results.
So today, in the match Arnaldi v Casanova, I recorded tennis_player1_service_breaks every 10 seconds, and this is what I got:
1024
17656
22927
14080
16173
16571
16173
14311
0
14311
1139
0
0
16571
16571
17656
14311
17656
0
22927
(this then went to 0 before the end of the first game, and stayed at 0 for the rest of the match)
I would really like to use tennis_player1_service_breaks in my strategy because the theory fits nicely, so could someone explain how I am supposed to use it please? I don;t understand these numbers.