Erased partition is still full

I have a 1TB Adata external drive that had 2 partitions, one of which I use for Time Machine backup. I erased the other one (New Backup); then removed the partition; then renamed it (Bootable Mojave) and created a new partition. It was never full, but now it is full of all sorts of things that were never there in the first place according to system information. The new name shows in the finder, but it shows almost nothing on it (checked with hidden items as below). And Disk utility shows something different. I ran first aid, which showed as successful, but still no change in the system info window. And when I tried to restore Mojave to that disk, it failed. What could be going on here and how can I fix it?