Today I experienced the difference between "yours" and "mine." I graded papers last week after I was told the scale was to be calculated by deducting 10% per grade.... no problem, I subtracted 10% from A to get A-, then from A- to get B+, and so on until you got to 40% and a D. I graded, recorded and handed back.
Then the professor sent out an email with the grade breakdown to the class. The professor's grade scale went like this: subtract 10% to get A, then 10% from A to get B, then 10% from B to get C.
As you can imagine, there were some questions. Long story short, I will be recalculating something like 40 grades in the next two days.