The size of grids is fluid, because the module is fully responsive. The most important facts:
1) The smallest grid element is 1x1 square, where "1" means 16.666666% in the desktop layout, 25% in the tablet layout and 50% in the mobile layout.
2) The width will be fluid, because the biggest width for the desktop layout is in example 1200px and the smallest is 840px, so one unit is in range "140-200px"