possible reasons for not all records transferring

Hi Experts,

I need some inputs reg this.i am loading data from Infocube to DSO.

Infocube has 75,000 records.

when i try to extract the records from infocube, only 45,000 records are transferring to DSO instead of all records. My understanding is first all the data whichever available in the source should be transferred to target and based on our routines, filters data will be filtered. What might be the reasons for not all records are moving to target initially/

Thanks,

anil