I'm transferring 10gb folder at 76.8KB/s. USB 3.0

[AV2RY]

Hey guys, I just installed W10 on my WinBook. I realized it made Windows.old folder sized 10gb, just in case I wanted to transfer it on external 500gb drive USB 3.0 (tablet also has USB 3.0) and delete it from tablet. It started ok but after 400mb it went down to 76.8 KB/s. It transferred 8gb by now, will I always have this issue? It's ridiculous. What's funny is since it completed 400mb it shows
99% complete
Items remaining 0 (0 bytes)
Time remaining: Calculating...
And still transferring files