Training Devices?

I have a question about the Promotion Test.

The rule says, "Promotion test: DiceY?" where Y = 5 + eir logic/10, rounding down. If this is strictly greater than their grade, they may add one to their grade..."

Does this mean Y = ( 5 + logic) / 10, which would result in promotions being nearly impossible? Or does it mean Y = 5 + (logic/10), which is far more attainable?