This is about the unit number on an address that has one — the PMB on your mailing address, or the lot number on a Basic Domicile or SavvyNomad residential address.
Yes — in general what matters is that the unit number is present. It can read as PMB, Lot, # or any common substitution.
If your address does not include a unit number, do not add or invent one. Domicile Premium residential addresses have no lot, unit, or apartment number, and adding one can cause mail to be misrouted or returned.