Hi Rudra,
most likely the following SAP Note can help: 1548125 - Interesting Facts about Inventory Cubes
That's a very good note with lot of information and examples how the OLAP actually handles and calculates non cumulative key figures especially in the inventory management scenario.
Generally remark: It depends if you use HANA optimized Inventory Cube or not.
In a not HANA optimized Inventory Cube maybe you have skipped the step to run the compression with "No marker update" after loading the historical movements OR
in a HANA optimized Inventory Cube maybe you have not executed the DTP with the flag "Historical Transactions".
In any case I would check the SAP Note and the referenced How To Guides.
Best regards and have a great weekend,
Andreas