Currently (as of v0.6) Aurora on first start scans Content and Cache folder for TU, fills the database and copies TUs it found to Aurora folder. When you set TU you like, it deletes TU in Content/Cache folder on Hdd and copies TU from Aurora folder to Hdd.  If you download TU from Aurora it puts it in Aurora folder and if you activate it Aurora deletes TU from Content/Cache and copies from Aurora folder to Hdd. All of that is time and space consuming as Aurora makes a copy of all