Anaerobics Training Effect calculation wrong

This can be a side effect of a major bug with this device: lhtr not being synced correctly. You will find dozens of threads on this forum. It's unlikely to be solved. 

What do you mean? can you elaborate a bit more? because I was on the track today doing intervals. Specifically: 1km 3 zone, 10 x 200m pace 3:00-3:30. I alternated it with a 2 minute rest in zone 2, at the end I had a 1km relaxation in Zone 3. You can see the result in the pictures.

Maybe you can elaborate more on your training session. Do you have the same training in the past ?

I had my intervals at the track. I am able to achieve >4 anaerobic load.

I have similar experience with mine as you do.  Depending on the structure of the workout it may be classed as Anaerobic Activity (3.5 and 3.0 in this sessions case) or VO2 Max (3.8 and 2.5) as the main benefit. The Anaerobic had more sets of shorter reps than the VO2 Max session , which sounds logical to me. Probably if I did record the WU and CD separately these metrics would improve even more.

Longer intervals (over about a minute) or ones that don't get your heart rate into Z4/Z5 may not be counted as anaerobic.