It can't. You can track resources either as individuals or as aggregates
(ie, 5 carpenters) but you can't list the same resource both ways. Joe can
be listed either as "Joe Woodworker" or be included in as an un-named one
of "5 Carpenters." The Resource Group field isn't use for assigning at
all - it's there to allow for filering and grouping when reporting.