Probably just a Friday brain fart, but a couple of dumb questions

... in a regular Form:

Set Form_Datatype to Number throws a compiler error
- Error 4306: C:\DEVKFP\DF19.1\Kirknet\Appsrc\POSWizDRBase.dg (ln 362) Forward reference not resolved MSG_NUMBER

it's listed as a value in the help for both 19.1 and 20 but I can't get it to compile
Same error with and without form_margin
same error with and without a form_mask

I've worked around it, but anybody got an example or is the help wrong?