Mismatch in report

hi experts,

i have report on 0IC_C03, that report shows difference between quantity of total stock and quality of total stock, based on storage location and grades, but in my report one of the grades showing minus value, but in R/3 there is no data in particular storage location and grade.

what is the problem,

where i can search,

please help to do,

thanks in advance,

venkat