event_id different in mf vs betfair?

As part of my strategy, I'm accessing betfair's API directly (outside of mf) to retrieve some event_ids, then I'm passing those event_ids to mf, using:
Selection's - Trigger Expression - "event_id" - is in file - filename.txt

Unfortunately, this hasn't been working, and after some debugging, I've noticed that the event_ids are (slightly) different.

Ie. current match in Betfair: Kerkhove v Ral Serban
In Betfair, the event_id is 31503676
In MF, the event_id is 315036766416

Because of the difference, there is no match and therefore no trade.

Can anyone tell me how to handle this, because I don't understand why they are different?