Adding Functionality to Your Cube - Getting Started with SQL Server 2012 Cube Development - page 167

Let us review the created calculation to understand the code used in the example.
First, the code starts with a normal case statement:
case
The next statement is a check that checks the level of the current member in the
product hierarchy; if it is 0 , it means that it is on the top of the hierarchy:
when [Product].[Product
Hierarchy].CurrentMember.Level.Ordinal = 0
If this is true , the value is set to 1 meaning 100 %:
then 1