Ok, I’m going to start this off as I am fairly new to running. I’m been at this for about 6 weeks now, but I feel like I am in reasonable shape as a starting point (27m 5k). I have my first official timed 5k for April so I have been working on a training plan in here. My question though surrounds the “Form” on the Fitness page. Should I be looking at the Absolute value or the Percentage of Fitness value? They show up very different as you can see from the screenshots below, I assume this is partially due to lack of historical data. Based on what I have read, I should try to keep Form in the Optimal range to improve my fitness level and ultimately better my 5k time. Unrelated, how high should I expect my fitness number to get after 5-6 months of training (I’m sure that is somewhat person specific).
Read here
As you seem to be reasonably fit with a 27min 5k, I’d say it depends on how you feel. Do you feel like the training you did was well manageable, i.e. not too exhausted all the time, no small niggles, no constant calf tightness etc? Then stick with the green version.
If instead it was very challenging, borderline severe, with you fighting every step? Chose the red, and bring your training down into the green.
At the end it’s just a model (maths) - all models are wrong, some are useful. 
I would say overall I feel very good. Many days on easy runs, even after going 6+ miles I feel like I could do more. I almost always feel very recovered within 24 hours. My Garmin regularly has my training readiness very high the next Morning like today (after running a 27m 5k last night). No major aches and pains. Obviously my calfs some day do feel like they put in some work, but nothing crazy. I often feel like I could do an easy run on my rest days. Currently trying for 4-5 workout days per week, which feels easy.
There you go - the “green” option is the one for you. 