Section 20 I think it is in the "new" Form filled in by the FFL holder. Take your lease agreement, some credit card statements, that prove that you cover 90 days of residency, they will confirm you have the right documentation. They might want to copy and store those documents too, its not required they can just record what the documents were. If you use Credit Card Statements, refuse to let them be copied, copies are not a requirement of the form, just a statement of the FFL of what that evidence was. You don't want to be the victim of Identity theft.
AFL has nothing to do with this form at all, it's a WA State tax on LPR's who want to exercise their 2nd Amendment right.