How is 40 hours per fortnight calculated in Austrlia

How is 40 hours per fortnight calculated?

An example of how 40 hours a fortnight is calculated:
After your course has started, you work the following hours over a four week period:

• week 1: 15 hours work
• week 2: 25 hours work
• week 3: 25 hours work
• week 4: 10 hours work.

In the fortnight comprising weeks 1 and 2 above (40 hours worked in that 14-day period) or in the fortnight comprising weeks 3 and 4 above (35 hours worked in that 14-day period), the work condition is not breached. However, you will have breached your work condition in the fortnight comprising weeks 2 and 3 above (50 hours worked in that 14 day-period). Students found to have breached their work conditions may be subject to cancellation of their visa.