What was your best 20 min interval from that ride?
Anything with a VI close to 1 will serve as a good indicator. VI of 1.27 is a lot of variability. Makes me thinks that you were riding in rolling terrain. Drilling it on the uphill and recovering on the downhill kind of ride. Not a very good test for aerobic strength because you're replenishing your anaerobic systems there as well. That said, your FTP is still set pretty low.