IFA011 and IFA014 specify cardinality of certain attributes as 1 or 1..N. That means, those attributes are required to have a value. For example, in VduProfile, there are two attributes, MinNumberOfInstances and MaxNumberOfInstances with a cardinality of 1.
In YANG, there are two ways to satisfy the requirement. Set the node to be 'mandatory true', meaning the value needs to be specified, or set a default value on the node.
The advantage of the second option is that no action is required from the operator, if they are happy with the default values. If they are not happy, they will need to change the default value. With the first option, an action is always required, i.e. the operator will have to assign a value. If they do not, the configuration is rejected.
These changes removes 'mandatory true' in certain cases, and replaces them with default values.