Hello,
in the download page, the offline CHM documentation is marked as Telerik_UI_for_WPF_ApiReference_2015_2_728.chm.
When the file is downloaded and opened, it says that the documentation is for the previous version: Assembly: Telerik.Windows.Controls.Input (in Telerik.Windows.Controls.Input.dll) Version: 2015.2.623.40 (2015.2.623.40)
Naturally, the new members are missing from the documentation...