Inventory Ageing report showing negative values

Hi All,

we have developed an Inventory ageing Report, in that if we take all the totals for quantity and stock value, those values are matching with the ECC Values, but if we take any other values like 0-7 quantity, 8-16 quantity (variables created using formula).......these are showing some negative values, but if we add all the values for a particular row(quantities(0-7 quantity,8-16 quantity......, stock values 0-7 stock value, 8-16 stock value..............), the total of positive and negative values is matching my Total quantity, stock value total.

Please see the below image for better understanding my problem.

can anybody help me on this issue... I am very new to this

Thanks in advance..

G S Ranmanjaneyulu.