legally importing HGH, what is 50 units?

[Zino]

So I was reading through this and as you can see you can legally bring in 50 dosage units without a script. Does anyone know what would count as one unit? Would it be one vial? One kit? One IU? Thanks!

21 USC 956 - Sec. 956. Exemption authority

(a) Individual possessing controlled substance (1) Subject to paragraph (2), the Attorney General may by regulation exempt from sections 952(a) and (b), 953, 954, and 955 of this title any individual who has a controlled substance (except a substance in schedule I) in his possession for his personal medical use, or for administration to an animal accompanying him, if he lawfully obtained such substance and he makes such declaration (or gives such other notification) as the Attorney General may by regulation require. (2) Notwithstanding any exemption under paragraph (1), a United States resident who enters the United States through an international land border with a controlled substance (except a substance in schedule I) for which the individual does not possess a valid prescription issued by a practitioner (as defined in section 802 of this title) in accordance with applicable Federal and State law (or documentation that verifies the issuance of such a prescription to that individual) may not import the controlled substance into the United States in an amount that exceeds 50 dosage units of the controlled substance. (b) Compound, mixture, or preparation The Attorney General may by regulation except any compound, mixture, or preparation containing any depressant or stimulant substance listed in paragraph (a) or (b) of schedule III or in schedule IV or V from the application of all or any part of this subchapter if (1) the compound, mixture, or preparation contains one or more active medicinal ingredients not having a depressant or stimulant effect on the central nervous system, and (2) such ingredients are included therein in such combinations, quantity, proportion, or concentration as to vitiate the potential for abuse of the substances which do have a depressant or stimulant effect on the central nervous system.

[Big]

...the Attorney General may by regulation exempt from sections 952(a) and (b), 953, 954, and 955 of this title .

the first thing that strikes me is the drastic difference between "may" and "will".
additionally, I see no conclusive statement that being exempted from the stated sections indicates an overall exemption.