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(a) and (b). The field is already a Number, so you may define the output field as a Number, taking care of the format you apply. If you define the output field as a String and you don't set a format, Kettle will send the field to the output as 1.0, 2.0, 3.0, etc., which clearly is not the same as your code. Just to confirm this, create a single file and a transformation to see the results for yourself.