Lots of people think using a layer mask is only for the advanced Gimp users, fortunately this isn't the case at all. Let me explain you the basic usage of layer mask on a easy to follow step-by-step example.
If you want your progress bar to look a bit different you can create it in a shape of a circle with counter in the middle. We will create in a so called flat design trend using Adobe Photoshop.
Capturing a screen of your iPad into an image can be quite useful sometimes, without that option, making this tutorial would not be as simple as it was.