Precision about cloud and Lightroom

Hello,

I'm sorry if my question is "silly" but I'm a new user of Adobe Creative Cloud Lightroom solution.

My question is the following and I cannot find a clear answer on the Adobe site. What is the practical use of the storage volume in the cloud?

In my case I have a SIN and I download all my photos on it. I integrate them into Lightroom Classic on my windows PC and synchronize my workflow to access them on the go via Adobe CC. By doing this my 20 GB of cloud are absolutely not consumed (about 1000 photos to date).

Should I deduce that the storage volume (20 GB in my case) is only used in the case where you want to download your photos directly on the Cloud and in this case I understand the interest of switching to 1 TB. because my iPad would not have enough storage.

Does it mean that if I have a local backup of my photos, I can synchronize an unlimited number of RAW photos while technically I exceed 20 Gb.

Or the fact of synchronizing my collections should still consume space and this is a bug with me?

Thank you,

PS: I'm French, sorry if my English isn't great.