Meaning of symbols within Addons / Manage dependencies

I’m on the latest Krypton RC, using the standard Estuary skin and wanted to remove addons I either don’t use anymore or which have been installed as dependencies and are no longer required. The former part is easy, with the second I’m not sure: When I go into Settings / Addons / Manage Dependencies I see the full list of addons. Most have a checkmark. Fine, I understand they are installed and activated. I suppose this are also the ones which are still required by the addons I installed. Then there are those which are labeled with some kind of brush(?) symbol. They are apparently active. And from the above I assume(!) those are addons I can remove since they are no longer required. Is this understanding correct? And what is that brush (or whatever it is) actually supposed to symbolize?