Music Status in iCloud?

Can anyone explain the icon - the little x in a circle and a cloud with a line thru it. Thy seem mutually exclusive.

I have a large music library on my hard drive, loaded from my CDs. I also have a large library of purchased tunes from iTunes. So I got iTunes Match. Not sure what it actually does, but I got it. Then I let the subscription lapse for a few months before I re-upped Match. Now I have those funny little icons on every thing piece of music I have. It doesn’t recognize my Music library so I can’t update. Also, I have multiple copies of most of the songs I play a lot. I’m sure I did it wrong, but how can I tell which ones to keep or delete when they have one of the icons?