The gray band indicates watts well below LTP and the target for recovery watts.
If you drop into that band the timer will slow way down (as though stopped) because you aren’t accumulating XSS in the recovery target zone.
It’s similar to the fact you can’t fill the Low bucket on Endurance days by coasting. 
Recovery is actually up to you. You don’t need to match it exactly.
You might, for example, decide to go again before Ready appears and rely on CL movement instead. Or extend how long you stay in Ready state and perform intervals in sets with breaks between sets.
I don’t think XMB on a Garmin has room for an additional power field. 
It’s possible on EBC but how would you use it?
Are you concerned about target compliance?
The target wattage is actually a range +/- the value shown. No need to be precise. 
On a Garmin as long as the circles intersect at some level, you’re within target range.
If you want to closely adhere to the central target concentrate on keeping the circles aligned (eclipsed). No need to monitor actual watts.
On EBC Android keep the arrow touching some part of the target circle or dead center for closer “compliance” but remember that’s relative.
If you consistently ride below or above the target range, XMB guidelines adjust to help you fill the buckets at an equitable rate.
Indoors in Slope mode you can be more precise about executing XMB guidelines to the letter (if that’s what you like to do) but the point is you don’t have to. 
Note: On a Garmin you can change the default power smoothing from 3 seconds under XMB Connect IQ Settings.
Reference –