According to the 1879 edition of Hart’s Annual Army List:
Lieutenant Hamilton William Wetherell Spooner, 94th Regiment of Foot, had 8 years service, and had spent 2 years and 8 months on Half Pay.
I imagine wherever Ray has taken the information from is where the error occurred.
MacKinnon & Shadbolt does not include the details of every officer who served in the Zulu War. A fact I tried to have incorporated in an introduction of the Greenhill edition that I was associated with, unfortunately that fact appears on the dust jacket fold. If you don’t have the dust jacket, the same information appears in the heading of my index.