From Quick Connect Admin guide it states the following:
• Process all data. If you select this method, each run of the step will process all data in the specified synchronization scope.
• Process delta from last run. If you select this method, each run of the step will process only the data that has changed in the specified synchronization scope since the last run.
Quick Connect does not have a feature to calculate and process delta. This feature is true ONLY is connected system supports the delta mode in this case Quick Connect will utilize this feature, for example is an Active Directory. You use special cookie in order to instruct AD to return only changed objects since last LDAP search. . In this situation AD returns list of changed objects and new value of cookie. Thus next time you can obtain next portion of changed objects.
This Quick Connect feature is supported ONLY with connected system that supports the delta mode.
NOTE: If connected system does not support delta mode (for example SQL or CSV file) then it is useless to use this option. Full sync will always be used instead.