Partitioned tables

Hello!

Please clearify me how table partitioning works in this example:

Suppose I created this function

CREATE PARTITION FUNCTION PartFunction (int)
as RANGE LEFT FOR VALUES (50);

and is adding it as a partitioned function in the Create Partition Wizard.

This page http://msdn.microsoft.com/en-us/library/ms188730.aspx says:

"6. ...

In the Select filegroups and specify boundary values grid, under Filegroup, select the filegroup into which you want to partition your data. UnderBoundary, enter the boundary value for each filegroup. If boundary value is left empty, the partition function maps the whole table or index into a single partition using the partition function name."

I don't understand why "If boundary value is left empty, the partition function maps the whole table or index" -the function I added in the previous screen already contained "RANGE LEFT FOR VALUES (50)", - why should specify the boundary value once again?

Thank you in advance,

Michael