Physical Quantity and Physical quantity units are two useful task properties to show construction quantities for tasks. Physical quantity and physical quantity units can be entered manually or created by script. For Physical Quantity Dependent Tasks, we can compute the task durations based on:
Now you have applied right rules to related tasks. It is possible to assign any rules (root/parent and leaf/child). You can also confirm which rule is assigned to the selected task, in Task Properties > Resources by expanding the Rules node.