Thanks for using GlassWire! Our help guide is here https://www.glasswire.com/help/.
The grey sections of the graph with a clock icon means that your PC was idle during that time period. This can be helpful because if you see a lot of network activity when your PC isn’t even in use it can sometimes indicate unusual behavior.
You can then click the graph to see what apps/hosts your computer was connecting to at that time.
More alert meanings are available on our alert dictionary page. https://www.glasswire.com/dictionary/