The Artillery Attestations ledger from which your image is taken has quite a few discharge entries from the 1930s, so I would interpret this as meaning that he served on after the end of WW1, and was discharged in 1937 when he would have been about 45 years old.
Having now seen the complete entry, I think some of the words above the reason for his discharge include RGA (Royal Garrison Artillery) and Farr Sgt since he was a farrier and the next line includes 4

Bde RA, so possibly his unit. Given that the handwriting is different for the two entires, I don't think they are necessarily linked.
Also I'm afraid Historical Genealogy quoted the wrong reason for his discharge. See the entry below. As the Army was being mechanised in the late 11930s it stands to reason that they would need fewer farriers, in the artillery.