Capacitor ratings aren't all that precise, but you can at least work out how imprecise the ratings are by deciphering the following letter tolerance codes.

Code Tolerance
B ± 0.1 pF
C ± 0.25 pF
D ± 0.5 pF
F ± 1%
G ± 2%
J ± 5%
K ± 10%
M ± 20%
Z +80%, –20%