I don’t feel that x/10 ratings can easily be ported over to the American grading system. To me, a 6/10 movie means it’s good but nothing too special. There is a difference between a 1/10 and a 5/10, whereas they would both be simple Fs if you went with grades.
True which is why I switched to letter grades because I could never shake the relation to percentage and most of my ratings fell within a smaller range.