'MinParentSize' and 'MinLeafSize' -- regression tree

https://uk.mathworks.com/help/stats/fitrtree.html

It introduces the MinParentSize below as:

Minimum number of branch node observations, specified as the comma-separated pair consisting of 'MinParentSize' and a positive integer value. Each branch node in the tree has at least MinParentSize observations. If you supply both MinParentSize and MinLeafSize, fitrtree uses the setting that gives larger leaves: MinParentSize = max(MinParentSize,2*MinLeafSize).

Example: 'MinParentSize',8

Data Types: single | double

My question is about this line: MinParentSize = max(MinParentSize,2*MinLeafSize). Why there is a 2*? And could you give me an example in this case?