The WAB (Wet arbeidsmarkt in balans) stipulates that as an employer, you pay less employer premium in certain situations.
One way to qualify for a lower WW premium is to pay employees under 21 a maximum of 48 hours per 4-week reporting period or 52 hours per calendar month reporting period.
Within the roster module in R&R, a counter is available that tracks the hours of these employees under 21, per reporting period. You can select this counter via Options -> WAB, after which the counter becomes visible for the employees who are eligible.