I'm under the impression that because it's button operated it has set adjustment increments. It changes in mm for the metric set and 16th of an inch for the SAE set. I had the same question at first.
Amazon has GearWrench 9900 7 Piece Flex-Head Combination Ratcheting Wrench Set Metric for 39.99 shipped if you have Prime. It should be free super saver shipping even if you aren't a Prime member too. I thought it was a good price.