In checking "Confederate Cemeteries" by Mark Hughes under botn MacMath and McMath:

Vol 1 shows:

McMath, W.T. Co A, 20th GA June 11, 1864 VA25
[VA25 is Richmond - Hollywood Cemetery]

Vol 2 shows:

McMath, C. Alabama VA57
[VA57 is Fredericksburg - Confederate Cemetery]

McMath, G. Co E, 60th NC died April 25, 1865 VA41
[VA41 is Petersburg - Blandford Cemetery]

I don't find a listing for John McMath.