This attribute controls the appearance of an annotated
coordinate grid (drawn with the AST_GRID routine) by determining
whether labels should be drawn to represent the numerical values
along each axis of a Plot. It takes a separate value for each
physical axis of a Plot so that, for instance, the setting
"NumLab(2)=1" specifies that numerical labels should be drawn
for the second axis.
If the NumLab value of a Plot axis is non-zero (the default),
then numerical labels will be drawn for that axis, otherwise
they will be omitted.