CBFM experts - can you explain....

[Gurraun]

how does the cbfm know when to expect my period in month 1? (I believe the m button will start flashing at some point). It asked me to start testing on day 6, had lots of highs but no peak until day 18 so did 20 tests (today is day 26 first with no test). Sadly doubt I'm pregnant as only dtd on both peak days so no doubt missed the boat, but would at least like to know when might expect af (came off pill in may and longest cycle been 29 days / shortest 24) so was alarmed not to ovulate until day 18 and now paranoid luteul cycle too short to get bfp. Hope in reality all just settling down (already lucky to have a cheeky 2 year old ds so know it all worked once.....).

Short answer is, it doesn't.
It guesses based on your OV date but it's only after a couple of months that it can make a prediction.
Don't worry about the highs but no peek. Common on the first month I understand.

As Pip says it's an educated guess but also it doesn't really mean anything as it just flashes away until you press M.

I think it's just supposed to remind you if you are late and haven't tested I think is funny as the chances are if you are using a CBFM you pretty much have these things tattooed on your brain

It flashes 14 days after your first peak.