Should I be worried about a hardware error if my MacBook Pro is running ok?
Rember only tested less than 1 GB of your 8 GB of RAM, as explained within the screenshot of the Rember application.


  Memory allocated for testing: 947 MB

Apple Hardware Test will test all of the RAM in the system, since it runs outside of macOS.


As also explained in Rember, to be able to test more RAM with the program:


  run memtest (the core of Rember) in single-user mode