Sales document No. do not reconcile between BW and ECC

Hi,

I have a report based on SD data source 2_LIS_11_VAHDR which shows sales document number and net value, It has filter on created on field (ERDAT)so the report only shows the sales documents which were created previous day.

So, when I compared bw data with the data from VBFA table from T-code se16n there are few records appears in the bw report which were not created yesterday but few months back and few records were in the VBFA table but did not appear in the BW.

1) Does anyone know whey certain records does not appear in the bw?

2) What do I need to do if I only want to see the sales documents which were created the day before?

Thanks

Darsh