Every pharmacy shall at all times when open be under the constant, direct and personal supervision and management of a pharmacist who shall have personal supervision of not more than one pharmacy at the same time; Provided, however, a person licensed as an “assistant pharmacist” under the laws of the Virgin Islands may lawfully be left in charge of a pharmacy only during the temporary absence of the pharmacist. For the purposes of this section, “temporary absence” means only an unavoidable absence which may occur during a day's work not to exceed two hours in any 24 hours and when the pharmacist in charge is within immediate call, ready and able to assume the direct supervision of the pharmacy.