How do I recalculate my Fitness Signature Progression? – Xert (baronbiosys.com)
The goal is to obtain a ballpark starting fitness signature and move forward from there.
As long as your historical data includes enough max efforts along your power curve that should be sufficient. Any required tweaks will occur from future activities.
Extract is an advanced function. I don’t suggest using it until well familiar with how Xert works and why you might use it in the future.
When to use the "extract"button in "advancede mpa"tab - General - Xert Community Forum (xertonline.com).
Lots of newbies tips are posted in this thread –
Beginner questions - Support - Xert Community Forum (xertonline.com)
Welcome aboard. 