SELECT
    CAST(CEILING((Sub.ActualAVG - Sub.FalseAVG)) AS INT) AS DIFFERENCE
FROM
(
    SELECT
        ROUND(AVG(CAST(SALARY AS FLOAT)), 2) AS ActualAVG
    ,   ROUND(AVG(CAST(REPLACE(SALARY, 0, '') AS FLOAT)), 2) AS FalseAVG
    FROM
        EMPLOYEES
) AS Sub