Hi,
Setup run for the BX is done to get the opening stock. This opening stock will be the stock on the day when you do the setup run.
if you run ur report for that day & check the stock in the ECC, it will match.
Setup run for BF is done to get the material movements. So the Here you can specify the dates. So whatever date range you specify when running the setup table, those dates stock will be visible in the report.
BR