I agree
@philly1991 the libre can be inaccurate, particularly when exercising as your bg levels are moving at a faster rate, the 20 min lag makes it difficult to use for accuracy when exercising, however it's still great for spotting trends and seeing the direction your levels are going in, so still a useful tool.
Basal fasting is recommended as getting the basal set at the right dose is the foundation for your control, so it's vital to make sure it's right before looking at your bolus ratios:
https://www.mysugr.com/en/blog/basal-rate-testing/ this is a good site to get you going, bear in mind the values are US so divide by 18 to get mmol/l values.