Workflow Rule - Message with Amount to Invoice

Below is a message I created for a workflow rule to notify end users they have an invoice ready for approval.  Does anyone know why my "Total Cost" is not working?  You can see it present in SQL with an amount and in the invoice.  

|"Subject Invoice has been issued and is awaiting your approval, do not delay!"|
|"Sign the attached document and send the copy to"|

|"Supplier: "+ [M:BIS0]BPRNAM|

|"Comments: "+ [M:BIS1]DES(0)|

|"Invoice Created on: " -format$("D:MM[/]DD[/]YYYY",[F:PIH]BPRDAT)|

|"Invoice Due by: " -format$("D:MM[/]DD[/]YYYY",[M:BIS1]DUDDAT)|

|"Total Cost: "+ [M:BIS1]AMTATI|