Some text fields are normal and boring, but Sketch's text fields incorporate a bit of magic in them. When you click on a text box you have a lot of options on how to change value inside of it. Holding the up and down mouse keys increases its value by one, holding Shift increases the value by ten while holding the option button down increases or decreases it by a tenth of that size. You also have the ability to scrub your value back and forth to get very precise without the need to re-type a value. As if this wasn't enough, Sketch also always you to do basic equations such as +, -, *, or / to do quick basic math with a concrete value to use.