Images imported into LrC are stored locally on hard drives. They do not automatically sync to the Adobe cloud unless you selectively do that (e.g. by adding the images to a synced collection), in fact the LrC catalog itself needs to be manually sync-enabled before any syncing can be done.
But even if you do opt to sync some of your images from LrC to the cloud, they are only uploaded in Smart Preview format (2560 pixels on the long edge), and Smart Previews synced to the cloud do NOT count against your 1TB cloud storage allowance.
Images that you import into any of the Lightroom apps (i.e. Lightroom Mobile, Desktop or Web) WILL upload automatically to the cloud, and thus will count against the 1TB allowance, but LrC is not part of that process.