Comically low on the track, going full out. Which seems to be a pretty reasonable claim.
Also consider that Tesla didn't sue for over 2 years after the episode first aired. The episode was in late 2008, and Tesla sued in March 2011.
Well, except for the part where apparently they didn't actually manage to run it dry on the track.
This said, it's fucking Top Gear. Their idea of a "serious" car review of the Renault Twingo is seeing if a car (undoubtedly not stock) can do a flip in a sewer tunnel. Their review of the Reliant Robin was only about how the car (again, modified), only flips. Somebody should have clued Tesla in.