xert and wko4

I am using both xert and wko4. I have some questions about some terms. I think that in wko4, the index expressed by frc is called HIE in xert, but in my case there is a big difference between the two indices. I want to know the difference between the two indicators.
Also, xert’s concept of LTP was very interesting, but I’m not sure how it is implemented in WKO4.
Can you help me?

FRC (“Functional Reserve Capacity”) is in principle similar to HIE. How it is derived is not public knowledge. You can use our calculator to see how HIE is established using MMP data. HIE is different than other measures of capacity above threshold in that it can never be fully expended. MPA provides a limit on how quickly HIE can be expended.

LTP is unique to Xert and offers a way to estimate your aerobic fitness.