Simple : SSAS Default Measure ?

Team ,  I bet this might be sounding very simple to you and would appreciate your insights on this .

It was my understandings ,

SELECT FROM 
[<<Cube Name>>]

is going to return first Default Measure ( Depends on its property  Might be Count/Sum/DistinctCount ...)  as it appears in the cube XML(A) definition  and this returns

276 .

But when i explicitly pick the first Measure that appears on Beneath my First Measure Group it returns :

SELECT [Measures].[Pt Count] ON COLUMNS
FROM [<<Cube Name>>]

Pt Count

164

So my Question here is what would be the default Measure  and how do we define it for a Cube .

Thank you !

Rajkumar Yelugu