Here's what I have on John W. Everett, F/50th Va.
Everett, John W. F/50Va Pvt
860/00/00 Cen Jno. W. Everett, 22, farm laborer, Amherst Co. B. Sligo, Ireland. Living with family of James W. Millner, 39. [50Va: 73]
862/04/18 Enl Amherst Co. and present on muster roll of new recruits for F/50Va [1]
864/05/12 KIA Spotsylvania C.H. [2] Sources [25, 864/06/04] [50Va: 173, 864/06/10] say missing. No Union POW record.
The numbers you ask about are my shorthand to identify the source of the information. So:
[1] denotes the info came from the compiled service records of the 50th Va in the National Archives
[2] A postwar book, Amherst Co. Story by Alfred Percy
[25] Newspaper, Lynchburg Daily Virginian of June 4, 1864.
[73] 1860 Census of U.S.
[173] Newpaper, Abingdon Virginian, June 10, 1864.
Was he killed at Spotsylvania C.H.? Postwar roster in [2] says yes; however, casualty rosters of his unit published in June 1864 newspapers list him only as missing. The fact that I could not find a Union POW record for him suggests that he was not captured, but does not prove conclusively that he was killed or captured.
Do you have any more information on him?