In all probability it means 6.8 pF
Usually, the nomenclature is this (hope I'm correct

):
* n = n pF (n = 1 to 82, giving a range from 1 pF to 82 pF)
* n1 = n * 10 pF (n = 10 to 82, giving a range from 100 pF to 820 pF)
* n2 = n * 100 pF (n = 10 to 82, giving a range from 1000 pF to 8200 pF, or 1 nF to 8.2 nF)
* n3 = n * 1000 pF (n = 10 to 82, giving a range of 10000 pF to 82000 pF or 10 nF to 82 nF)
* n4 = n * 10000 pF (n = 10 to 82, giving a range of 100000 pF to 820000 pF or 100 nF to 820 nF)