From the TRX website:
The TRX 40/40 Challenge combines two signature TRX exercises we use to measure upper body and core strength: the TRX Atomic Push-up and the TRX Low Row. At our events, we have competitions to see who can get the most of each of these exercises. If someone can get more than 40 good reps, there's a good chance they are going to win! Also, we’ve been known to break out the 40/40 Challenge during our lunchtime workouts here at FAI headquarters.
I think I will have another go at it later in the week.