Completely separate score -- out of 8. It does not impact your 800 scale score.
There is no partial credit on IR -- so you will need to get all drop downs / radio buttons correct to get credit for that question. That said, you don't need to get all questions correct in order to score an 8/8.
For more information about IR scoring and to test out sample IR questions, check out:
www.gmatpill.com/gmat-practice-test/gma ... reasoning/