how to change default size of c# generated store procedure

Hi all,

i am trying to write c# store procedure which returns me a binary data it looks as below

  public static void SqlStoredProcedure2(string name, out byte[] backup)

and generated sql looks like below

CREATE PROCEDURE [dbo].[SqlStoredProcedure2] @name [nvarchar](4000), @backup [varbinary](8000) OUTPUT
AS EXTERNAL NAME [Database1].[StoredProcedures].[SqlStoredProcedure2];

from where these 4000 and 8000 comes from ? i need to change these as my data size is above 8000 , how i can do that,

i want to put some variable data size if possible if not some large value.

i am using sql express 2012 and vs 2012.

thanks in advance ,