In player settings under Icon section Tile's "Short name" is limited to 13 characters although in https://msdn.microsoft.com/en-us/library/windows/apps/br211427.aspx says that Short Name can be up to 40 characters length.

Steps to reproduce:
1. Create new project.
2. Change platform to Windows Store.
3. Open Player Settings.
4. Under Icon section try to write Short Name longer then 13 characters.
5. The end of the name gets cropped.

Tested on 5.1, 5.3.4p4 and 5.4.0b15.