17.14.4 /SUM

[DISPLAY\]SPECTRUM OutSpec InCube [Mask] /SUM [/CORNER Imin Imax Jmin Jmax] [/PLANE First Last]

Indicates that we are computing an integrated spectrum. The result corresponds to the integral of the signal over the valid area (sum of values times the pixel size in user units).

/SUM is typically used to compute integrated flux from Jy/Beam units. /SUM is exclusive of /MEAN.