If you are using a pen, stylus or finger with Surface’s touch screen and sometimes the screen senses don’t work accurately, you need to calibrate your touchscreen and adjust accessibility settings and programs.
How to calibrate touchscreen with pen on Surface Pro Windows 8
* Swipe in from the right edge to open charms bar.
* Tap Search. Type calibrate into the box, tap Settings, and select Calibrate the screen for pen or touch input from the results.
* In Tablet PC Settings window, go to Display tab. If you are using multiple monitor, select the one shown in the Display field you want to calibrate. Then tap on Calibrate button, and follow the on-screen instructions to do.