Total usage consists of stuff uploaded by Lightroom CC plus "Your Work", the Dropbox-like CC web space - https://assets.adobe.com/assets/recent. As that is empty, you must have accidentally uploaded files by Lightroom CC.
What plan did you subscribe to? How much storage is it giving you?
And which version(s) of Lightroom are you using? If "I am very happy keeping them only on my hard drive and backups", then you should be using what about call "Lightroom Classic CC", the original version of Lightroom. This is in Adobe's Photography Plan.
But by "newest Lightroom" do you mean that program that Adobe confusingly named "Lightroom CC"? If so, then everything is stored in the cloud, whether you like it or not. That is simply how it works. It is the only program that you get with Adobe's Lightroom Plan.
Go into Help > System Info, and copy the first line.