Problem with decimal precision in SQL using Linq to SQL

Question

I have a simple query:

var results = from k in db.tree_nodes
              join s in db.stocks
              on k.tree_nodes_id equals s.tree_nodes_id
              into tmpTable
              from rowtmp in tmpTable.DefaultIfEmpty()
              select new
              {
                  stock = (rowtmp.amount == null) ?
                           ((k.code == null) ? (decimal?)null : (decimal?)0)
                           :
                           rowtmp.amount - rowtmp.amount_in_use,
              };

This is the generated SQL code:

SELECT 
    (CASE 
        WHEN ([t1].[amount]) IS NULL THEN 
            (CASE 
                WHEN [t0].[code] IS NULL THEN CONVERT(Decimal(33,4),NULL)
                ELSE CONVERT(Decimal(33,4),0)
             END)
        ELSE CONVERT(Decimal(33,4),[t1].[amount] - [t1].[amount_in_use])
     END) AS [stock]
FROM [dbo].[tree_nodes] AS [t0]
LEFT OUTER JOIN [dbo].[stocks] AS [t1] ON [t0].[tree_nodes_id] = [t1].[tree_nodes_id]

The problem is, the generator created Decimal(33,4) when converting the results. So I'm getting "123.4560" in results instead of "123.456" All of my fields in this query are decimal(14,3). I don't mind the 33 part but I need to change the ,4 to ,3. How can I do this?