I believe it's an error in the manual (outdated reference). I have flagged it up to management for correction in the next printing.
While these outlets are handy to have if you need them, I would caution against using a 12 volt compressor with one unless you wired it yourself with heavy gauge wire and fuse. I believe those a compressor with the pressure and volume to blow-out the lines may pull some heavy current.
As Alan did, they are pretty easy to install, depending on where you need one. In the UDC would be handy for that compressor. Just buy a higher current rated receptacle and wire it straight to the battery with a fuse inline.
Sorry for the error.
Jim