To be certain you are configuring `tempdb` file sizes as *intended*, you should use T-SQL instead of the SSMS user interface.  

To resize files, you can use something like this:

    ALTER DATABASE tempdb
    MODIFY FILE (NAME=tempdev, SIZE=1GB, GROWTH=1GB);

You'd need to execute this once for each logical file in tempdb.  `NAME=tempdev_2`, `NAME=tempdev_3` etc.

I'd suggest using a T-SQL query to obtain information about the file sizes, as in:

    SELECT DatabaseName = d.name
    	, DBFileName = mf.name
    	, DBInitialSize = mf.size
    	, Growth = mf.growth
    	, GrowthIsPercentage = mf.is_percent_growth
    	, FileType = mf.type_desc
    FROM master.sys.master_files mf
    	INNER JOIN master.sys.databases d ON mf.database_id = d.database_id
    WHERE d.name = 'tempdb'
    ORDER BY d.name, mf.name;

As mentioned in the comments, you should certainly look into the possibility of using Trace Flag 1117 and 1118, if you are concerned about `tempdb` performance; ostensibly this is the root-cause of your questions about `tempdb`.

Aaron Bertrand has a great article about using the SSMS Interface vs T-SQL at http://sqlblog.com/blogs/aaron_bertrand/archive/2009/10/14/bad-habits-to-kick-using-the-visual-designers.aspx