A more thorough explanation:

A noncareer vice-consul is a consular officer who is appointed without examination and is not a member of the Foreign Service. They are subordinate to a consul and may be temporarily substituted to fill the place of a consul who is absent or has been relieved from duty.

When the consul was on vacation, a noncareer vice-consul was appointed to take over his duties temporarily.

This example illustrates how a noncareer vice-consul can be substituted for a consul who is absent.