This object counts the number of labels that are in
use at this point in time on this interface in the
incoming direction. If the interface participates in
the per-platform label space only, then this
instance of this object MUST be identical with the
instance with index 0. If the interface participates
in the per-interface label space, then this instance
of this object MUST represent the number of of per-
interface labels that are in use at this point in
time on this interface.