Each time a casual employee is required to attend for work, the employer must engage them for, and pay them for, a minimum of 2 consecutive hours, even if less work is actually done. The minimum attaches to each occasion of attendance, so two separate call-ins on the same day each carry their own 2-hour minimum.
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.