WelcometoMayoConnect, @marlenec we loveto help peoplesolve the puzzlesofmedical jargon, but this is probably a time you will need to contact the doc. The grades are based on percent of slippage. That would vary based on the size of your vertebrae.

Here is an explanation of how it is calculated and what the grades mean: https://www.spineuniverse.com/conditions/spondylolisthesis/spondylolisthesis-back-condition-treatment

Can you see the doctor notes on line? If not, you might want to call and leave a message.
Sue