Arithmetic overflow error converting expression to data type nvarchar. 'Company Info' (CINF) (CINF)

hello Expert i am facing the above error while executing below stored procedure in transaction notification.

IF @transaction_type = 'A' AND @object_type = '13'

BEGIN

DECLARE @FreInv NVARCHAR SET @FreInv = (SELECT ((((T1.DocTotal+T1.DiscSum)-T1.RoundDif) *.7/100) + T1.RoundDif)

FROM OINV T1 WHERE T1.DocEntry=@list_of_cols_val_tab_del )

If exists (SELECT T0.DocEntry FROM OINV T0 Inner Join INV1 T2 On T0.DocEntry=T2.DocEntry

WHERE @FreInv < '0.00' AND T0.DocEntry=@list_of_cols_val_tab_del)

Begin

SET @error = 122 SET

@error_message = 'Test Error'

End

End