Is field 2 a calculation field? Might it specify a result type of number instead of text?
Field 2 is a text field. If I sort on 1st field, I get all 4 choices in numeric order, plus "other" since I expect to add to the list with usage. The table associated with popup was imported, but it is text. I have attached the source table, Jobs. The popup uses Job ID & Name fields.
PS. I originally posted with "text" and "number" reversed in my original response here. I spotted the error and immediately corrected, but if you are reading my responses via email, you would not have seen my correction so apologies if that caused some confusion here.