I have this Same problem and the Format I am trying to change is NOT a measure, but the Summation Value of an actual Field [Value] from my query table. Despite the fact that the Field is defined as a whole number, the Value Summation in the MAtrix displays it as a a two digit Decimal Number. The paint brush formatting tab allows you to change the font, font size, color, etc. of the the Value Parameter in the Matrix, but does not list number format as an editable parameter. How can I edit the Sumation Value number format without the complication of defining a new measure, creating a new query, etc?