The colored bars near the left edge will give you the general overview when network requests to particular hostnames are all blocked (reddish), all were allowed (greenish), or some were blocked some were allowed (yellowish).

+, -: under 10 network requests were allowed, blocked.
++, --: under 100 network requests were allowed, blocked.
+++, ---: 100 or more network requests were allowed, blocked.

https://github.com/gorhill/uBlock/wiki/Quick-guide:-popup-user-interface#the-overview-panel