Hours to Recovery compared to body battery

I don't understand ....

It's now 10:30am. My fenix 6x pro says time to recovery is 7 hours (after a heavy Personal training session yesterday) but body battery is now 27% after 7.45 hours sleep

So I'll be fully recovered by 5:30pm today but there's no way my body battery is going to be fully recharged any time in the next 48 hours even if I sit in a chair all day and get 2 x 8 hour sleeps!

How does this work?