Difference between GR & GI qty

Hi All PP Gurus,

Can anyone tell me the answer of this

Material BOM of Parent part No. 25250310793460 is having only one

component (Child part no.25250310793450) of quantity one.

As a result of regular booking (backflushing) of subject Parent part in the month of January 2008 GR of parent part is showing 3766

and GI of child part 3220. Diffrence in GR and GI is reporo quantity.

But the repro quantity is not showing in the system.

so please tell why it is showing difference in GR and GI qty.