In the early 1920's the Royal Navy was being downsized and men were offered a £20 bonus in order to encourage them to leave the navy before the expiration of their term of enlistment.
That process was referred to as reduction, being discharged to shore was Royal Navy speak for becoming a civilian.
The regulation dealing with early discharge at that time was AFO 1359/22 = Admiralty Fleet Order 1359 of 1922
http://discovery.nationalarchives.gov.uk/details/r/C2707851His record says Shore AFO 1359/22 with bonus on reduction that was in June 1922
The remarks says that he passed a seamanship exam in March 1922 the £20 bonus refers to his early discharge bonus.