Pressing + or - on the number pad doesn't allow character entry the same is it does when pressing the equivalent keys on the standard qwerty part of the keyboard to the right of the 0 on the number row. This issue has been reported before through the forums and was logged in PITS but somehow wasn't carried over to the new feedback portal.

Related forum post: http://www.telerik.com/forums/dash-on-number-keypad-doesn-t-work-radmaskedtextinput

Original PITS URL: http://www.telerik.com/support/pits.aspx#/public/silverlight/14543

As a side note, the PITS items really should have been migrated over to the new portal and the ids should have been mapped so that the URLs scattered throughout your forum, peoples blog posts, and bookmarks are not dead.