I assume working to target ranges is most useful for assisting T1s and other insulin users in managing doses?
As a T2 originally on metformin and currently diet controlled I've used target ranges for the times I used my original (uploaded to PC) Libre logs, but I've been able to do something similar for very much longer using my meter's finger prick logs. My Contour Next has a Trends option which I can use for HbA1c predictions, but more useful is that I'm able to set (and adjust) individual target ranges for my fasting, pre, and post meal tests, showing number of results for each that are in, above or below targets over 7. 14, 30 and 90 day periods. and I found this invaluable when originally learning to manage my diet and glucose levels. (The fact that I could modify ranges up or down was a great help initially!)