When you first load,The slots on readonly area still can be open.After selected a Appt on readonly area ,the slots onr eadonly area become disable(read only).
When you seletced a appt on left area ,the slots on right area are enable open.

The issue can be observed following this - http://demos.telerik.com/silverlight/#ScheduleView/SpecialSlots.

Available in LIB version 2016.1.201, it will be also available in the 2016 SP1 Release.