If u consider 140 weeks then number of days served 140 x 7= 980 days. number of leaves = 115 entitlement of leaves = 980/6= 163.33 days.
If u consider 139 weeks then number of days served 139 x 7= 973 days. number of leaves= 122 entitlement of leaves = 973/6 = 162.166 ays.
as your actual leaves are 120 which is close to 122, I prefer 139 weeks as served.
make sure weeks & leaves match exactly totaling to 1095 days. better always adjust ur leaves than adjusting weeks served.
refer this link. /forum/articleship-leave-calculation-47716.asp#.VOdbA52UeSM