Hi Fernando, thanks for sharing! Good efforts!
Your 20 min effort almost perfectly matches my explanation given in another thread (here).
In short, Xert is seeing that at the tail end of your 20 minute effort, you still had the MPA (capacity) to put out your best/highest power effort for the entire effort. If your TP was lower (like ~240 W), then you wouldn’t be able to have such a powerful surge at the end. Other platforms are unable to pick up on this since they’re only looking at the average 20 min power. Check out the post linked above for my full explanation. 