The FTP in the production firmware is based on 4 minutes Power(this value becomes from the track). 4 minutes is a really good indicator.
The question is that is not super accurate specially for endurance: you can have good 4 minutes but after that the Power can drop a lot.
If you have a look of the critical power chart of 2 different riders you can have the same 4 minutes power but the sprinter has hight values on short time and the climber the opposite.
In the new firmware (the one you are riding now) we monitor by a slinging window mechanism all 30sec, 4min and 16 minutes. For each rides, realtime for each second.
This allow the PC8 to manipolate data and have also short and long power spectrum.
Note that 16 minutes is a really long time since means 16 minutes wide open gas! And is not super common during the train/race.
All those 3 parameters are related to the date you got the best XXXCP and as soon ad those parameter are increased the FTP in increased too or, if they go out of scope (4 weeks) they will be re-integrated by the second best value. This is all inside the PC8.
FTP is based on W'.