If you work varying weekly hours or you work shifts of varying lengths you should convert your annual leave entitlement into hours. This is done by multiplying the number of annual leave days by 7.5 hours.
Example
24 annual leave days multiplied by 7.5 hours  =  180 hours.
Each time you take annual leave, the number of hours you would normally have been rostered to work on the day(s) taken should be aggregated to determine the amount of annual leave taken.