reckoner
The tape is asked for on the first of the month and the first of the month does not move. A month you were away, ill, or simply not thinking about it is a month with no reading in it, and that is the whole of what happens.
Reckoner asks again on the next first. It does not ask twice to make up the difference, it does not carry a missed reading forward, and it does not treat the gap as a signal about you. A prompt is due in a month you have neither logged in nor dismissed, so the month after a miss is an ordinary month.
What the gap does to the line
Nor does a miss quietly become the new schedule. The date is fixed rather than counted forward from your last reading, so a month off does not shift every future prompt a month later. Whatever happens, the next one is the first of the next month, which is the property that makes a series of these comparable at all.
Your chart draws straight through it. That is deliberate and it is worth understanding, because the opposite would be easy to assume: a gap between two tape readings is the cadence working rather than a hole in the record. Two readings eight weeks apart are two real measurements taken eight weeks apart, and the line between them says what it says.
The one thing that genuinely breaks a line is a reading you took back. Withdraw one and the line stops there and starts again on the other side, because a withdrawn reading is you saying that number should not be read, and drawing across it would be the software guessing at a measurement nobody stands behind.
What a long gap costs you is resolution rather than accuracy. Two readings a quarter apart tell you the direction over a quarter and nothing about the months inside it, which is fine if the direction is what you were after. If you want to know when something started moving, you need the readings to have been there when it did, and no amount of taping now recovers a month that was not measured.
And if the asking itself is the problem, that has an answer of its own. Press Later three times running and Reckoner asks whether it should stop asking altogether. Say yes and it stops. Your card stays where it is with your figures on it, and you can still tape whenever you like. The switch to start it asking again is on Setup.
That is the short version. The whole decision, with the numbers, is in How to take body measurements that tell you something.