Air carrier pilot reported after recovering from GPS jamming they had reduced navigation capabilities.

Narrative

Departing TLV we ran the GPS INTERFERENCE Supplementary Checklist. The first couple pages worked great and we departed TLV. Entering Romania Airspace we picked up on page X of the checklist; where we selected:GPS interference is no longer known or suspected; and the GPS has recovered * YES. Then when getting to page Y:Either of the following is True- GPS interference is not known/suspected during departure airport operations; but is suspected during OTHER PHASES of flight.- GPS interference continues after departure airport operations and/or the GPS has not recovered* NOThe remainder of the XX pages indicated the checklist is complete. The problem is that page XY is where we turn everything back to normal; and resume GPS updating. This page is not completed; leaving the airplane in a reduced ANP status for the duration of the flight; including the oceanic crossing. We completed the items on pages XY and XX and called the checklist complete. After resuming GPS updating; our ANP dropped from 0.4 to 0.04. The remainder of the flight was completed without incident.