This statement is set because those appointments that are recurrent and the Master appointment starts before the visible range and their occurrences or exceptions are part of the visible range. If they are not loaded some appointments may not be loaded event though they should be.
Hope this will explain the issue.
All the best,
the Telerik team
If you want to get updates on new releases, tips and tricks and sneak peeks at our product labs directly from the developers working on the RadControls for ASP.NET AJAX, subscribe to their blog feed