UPDATE: I got it. There is no bug here. Somehow got confused. 40 minute interval includes more of higher intensity work than 30 minute one.
ORIGINAL ISSUE:
Take a look at this workout personal records graph:
It shows 206W for 30 minutes and 209W for 40 minutes.
How is that possible? In my understanding it should be at least 209W for 30 minute interval.
I see this problem also in other workouts.
I already wrote to support@trainerroad.com but decided to take it also here.
I’m not sure what is wrong here? There definitely isn’t a problem but I’m not sure how best to explain it to you…
If you did 1 minute at 300 watts, 1 minute at 100 watts and then another minute at 300 watts, the average for 2 minutes would be 200 watts but the average for 3 minutes would be 233 watts.
That’s the basis for how longer time-frames can have higher averages.
Mike
Oh, now I get it. 
…
If the best 40 minute interval has a dip in power in the middle, then it may not be possible to find a 30 minute subset of that 40 minutes that has the same average power. If you think as the 40 minute interval as two peaks either side with a dip in the middle, a 30 minute window might only be able to incorporate one of the peaks thus giving a lower 30 minute average than 40 minute average.
