The filters you set in R3AC1 for adapter objects are stored in table CRMFILTAB on the ECC.
However in order to make filters work for adapter objects, there are certain entries that need to be maintained in CRMMAPTAB and CRMINTBAP which generally come as default.
And finally to enable filtering you need to have a parameter CRM_FILTERING_ACTIVE for adapter objects(individually) in ECC table CRMRFCPAR.
So to answer your question, delta load reads the tables mentioned above in order to filter the data.
And it al comes down to the filters you set in R3AC1 