The Tabata interval is 20 seconds of work followed by 10 seconds of rest for 8 intervals.
Tabata score is the least number of reps performed in any of the eight intervals.
Chris Spealler 40.
WOD Demo with Chris Spealler and Miranda Oldroyd - video [wmv] [mov] [HD mov - Download only]
The link below is with John Gilson of Again Faster as he's using James Hobart to demonstrate good and bad technique.