It is completely arbitrary in the US too. Most parents will berate their children for getting a B- or C in grade school, even if that translates into 77 - 82% of some complicated problems done correctly. There were some courses I had in college where showing up and doing the homework guaranteed a 90% and the last 10% was just test grades. They might have been low 100 level courses, but someone gaming the college system can get a 4.0 GPA taking all low level courses except the bare minimums to get their choice degree, have less knowledge than someone with a 3.5, but get hired easier because the GPA is high.