Сбой выполнения хранимой процедуры

У меня проблема с описанной ниже процедурой.

Ошибка:

Msg 402, Level 16, State 1, Procedure Get_FormattedBankStatement, Line 87. The data types nvarchar and nvarchar are incompatible in the subtract operator.

USE [K2_Objects]
GO

/****** Object:  StoredProcedure [K2RestSrv].[Get_FormattedBankStatement]   Script Date: 2/27/2019 5:00:12 PM ******/
SET ANSI_NULLS ON
GO

SET QUOTED_IDENTIFIER ON
GO



ALTER PROCEDURE [K2RestSrv].[Get_FormattedBankStatement]
--Declaring input parameter variable
@OpeningBalance Decimal(18,2),
@jsonValue nvarchar(max)

AS

BEGIN

        DECLARE
        @TotalCount nvarchar(150),
        @MinRowNum int, @MaxRowNum int,
        @DebitRecord nvarchar(150), 
        @CreditRecord nvarchar(150),
        @NewBalance nvarchar(150),  
        @PreviousBalance nvarchar(150);


        --Creating Temp Table #GetRowID
        Create table #GetStatement
            (ID int identity(1,1),
            PostDate nvarchar(150),
            TransDate nvarchar(150),
            ValueDate nvarchar(150),
            TransID nvarchar(150),
            Narration nvarchar(max),
            Debit nvarchar(150),
            Credit nvarchar(150),
            Balance nvarchar(150));


        --Inserting into TempTable #GetStatement Temp Table, from the select statement
        INSERT INTO #GetStatement 
            (PostDate,
            TransDate,
            ValueDate,
            TransID,
            Narration,
            Debit,
            Credit,
            Balance)

        SELECT
            max(case when name='post_date' then convert(nvarchar(150),StringValue) else '' end) as [PostDate],
            max(case when name='tran_date' then convert(nvarchar(150),StringValue) else '' end) as [TranDate],
            max(case when name='value_date' then convert(nvarchar(150),StringValue) else '' end) as [ValueDate],
            max(case when name='tran_id' then convert(nvarchar(150),StringValue) else '' end) as [TransID],
            max(case when name='narration' then convert(nvarchar(150),StringValue) else '' end) as [Narration],
            max(case when name='debit' then convert(nvarchar(150),StringValue) else '' end) as [Debit],
            max(case when name='credit' then convert(nvarchar(150),StringValue) else '' end) as [Credit],
            max(case when name='balance' then convert(nvarchar(150),StringValue) else '' end) as [Balance]

        FROM parseJSON
        (
        @jsonValue
        )

        WHERE ValueType IN ('string','real','int','object','array') and Object_ID is NULL

        GROUP BY parent_ID;


        --Selecting the first and Last RowNum from the TempTable

        SET @MinRowNum = (SELECT Min(ID) FROM #GetStatement)
        SET @MaxRowNum = (SELECT Max(ID) FROM #GetStatement)
        SET @PreviousBalance = @OpeningBalance;

        WHILE @MinRowNum < @MaxRowNum

            BEGIN

                SET @DebitRecord = (SELECT Debit FROM #GetStatement WHERE ID = @MinRowNum);
                SET @CreditRecord = (SELECT Credit FROM #GetStatement WHERE ID = @MinRowNum);
                SET @NewBalance = (@PreviousBalance - (@DebitRecord + @CreditRecord));

                UPDATE #GetStatement SET Balance = @NewBalance WHERE ID = @MinRowNum;

                SET @PreviousBalance = (Select Balance from #GetStatement where ID = @MinRowNum);
                SET @MinRowNum = (@MinRowNum + 1);

            END


    Select ID, PostDate,TransDate,ValueDate,TransID,Narration,Debit,Credit,Balance from #GetStatement;



END



GO