As manual input in a form.
All my tests were in Firefox. I often forget that Firefox’s input fields in Appsheet are sometimes different from other browsers, or the mobile app itself. Yes, I see now that Chrome, as well as the mobile app, prevents a 3-digit input. Firefox allows full manual input, or rather, requires it.
Hmmm. Doesn’t really answer the question though. Sure, it’s good that the input modal only allows valid input in those cases, but that’s different from actually detecting and invalidating any bad input before allowing the record to save.
I guess I should also say that the impetus for my investigations here was because I had a user run into a sync error due to a 3-digit second input. I can’t say for certain, but they should have been using the mobile app. I suppose I still have no idea how, why, or even if they manually entered those 3 digits. But I think something is off here, regardless.