Comment by JdeBP

It being 1982 and a story about the lead developer of LisaGraf, working on that very thing, it is certainly unlikely to be a GUI form.

But block mode terminals that did forms had been a thing for over a decade at that point. Not that this was likely at Apple. But there are definitely contemporary ways in which one could have been entering this stuff via a computer.

Indeed, an IBM 3270 could be told that a field was numeric. This wouldn't have the terminal prevent negative numbers. The host would have to have done that upon ENTER. But the idea of unsigned numbers in form data had been around in (say) COBOL PIC strings since the 1960s.

* https://ibm.com/docs/en/cics-ts/5.6.0?topic=terminals-3270-f...