Classification System (CTBW)

I have created a DataSource (1CL_OEQU001) in CTBW to extend the DataSource ZEQUIP_ATTR. I have added some characteristics.

When I carry out a test extraction in RSA3 for ZEQUIP_ATTR I get 5062 records selected. If after this I carry out a test extraction in RSA3 for 1CL_OEQU001 I get 12 records selected. In both cases the Update Mode is full. Could someone explain the discrepancy and how to fix. Thanks in advance.