We have resolve our problem on this... just follow this steps
Right click on your Desktop>click on Display settings
On Settings drag the "Change the size of text, app, and other items:100% (Recommended)" to 125% or to any scaling your comfortable with
then click the "sign out now" (text in red)
i think this has something to do with DPI Scaling. my friend has also experiencing the same problem, not just Arcmap but also with some other programs as well, with his newly acquired windows 10 laptop and we are trying to resolve the problem. i've googled it and found this info on the net. perhaps it could help you as well: pls follow this link... https://geonet.esri.com/thread/170386 or this http://www.tenforums.com/tutorials/5990-dpi-scaling-level-displays-change-windows-10-a.html
I've ran into that same problem before. i upgraded my laptop from windows seven to windows 10. but when i finished installing all the necessary drivers, especially the graphics card driver, my problems were solved. you can check if your graphics card driver were up to date. if not, update it to the latest version...