MAX goes over all the values you provide in a set of brackets, each separated by a comma, and returns the highest value.
MAX can also return the highest value of a list of values produced by another function.
This expression will always return the value that is higher, whether that is the actual or the expected amount of assets under management for the entity.
This expression works in a couple of steps to bring you the result:
MAX( .... ) is the overarching function, of which you want the result. In between its brackets sits another function.
get_properties_from_instances(.......) is the function inside the
MAX brackets, which goes and fetches the property of the instances you specify.
instances(AccountHolder, personal_income) returns the personal income of all the accountholders.
Since there could be no account holders, we add 0 as a default value to return.
These four combined, give you the single highest value out of the personal incomes for all the accountholders in the case.