So I rather blindly upgraded from Mojave to Catalina as I usually do when a new OS releases, which of course rendered my Adobe collection and numerous other apps unusable. Lesson learned. So I downloaded Mojave to a formatted USB drive, rebooted the system using Recovery Mode and Disk utility, and erased the drive labeled "Macintosh HD" containing OS Catalina.
Or so I thought.
After rebooting again while holding down option, I selected the flash drive with the Mojave Installer. So now I'm back on Mojave, but now there's this secondary volume entitled "Macintosh HD-Data." And what's worse, both Macintosh HD and the Data volume only show 14 GB free of 120.47GB. What am I doing wrong here? I've already backed up all my important files and apps on an external drive, and I'm just trying to get to a clean, blank slate. Any help would be immensely appreciated.
13-inch Macbook Pro (Retina), early 2015, 120 GB, yadda yadda.