On the User Parameters page, there is an option named< whether to consider units when IGS is read >.

         The default option is < Read length unit (including units) >, that means you’ll get actual dimension of the drawings; However, if someone ignores the unit when drawing,  for example, if the 50mm square tube is wrongly drawn as a 50inch square tube, you can select < Ignore length unit > before importing the drawing. When importing the drawing, TubesT only extracts the value of 50, and automatically matches it with millimeter as the unit, finally the actual import will be 50mm.

        The following figure shows the imported results of 50inch square tubes  by < Read length unit(including units) > and < ignore length unit > respectively.