Crack or a scratch?

Yesterday I was using a sander to sand my floors. Maybe 3 hours of continuous sanding. Heavy vibration from the sander. I had my 6 series watch on but it has a protective case on it. Afterwards I noticed this weird crack or scratch. Could this happen from vibrations? Or is it something else? Wondering if anyone has experience with this? Apple asked if it was cracked or scratched. What is the difference? It is deeper than a surface scratch. Seems my only option is a screen repair at my expense ($300, OUCH!). Thanks in advance.