There are two pass grades - Pass and a First.
The examiner has a scoresheet where he will grade your riding on a wide range of different factors. The obvious ones are safety, IPSGA (system), smoothness & speed, cornering, town riding etc. However, he will also grade you on "machine sympathy" (over-revving the engine), courtesy to other road users etc.
If you score 1's (highest grade) and less than three 2's on your test, you will be awarded a FIRST.