See http://stackoverflow.com/questions/22028358/scoreattained-condition-throws-arithmatic-exception-optaplanner

Due to the context where divide is used (calculateTimeGradient()), we might want to forgo typical rounding (HALF_UP or HALF_EVEN) and go for conservative rounding (FLOOR).

In any case, follow the behavior of Double/Long/Int calculations (which is floor IIRC)