I already answered to this query in duplicated support ticket created by you - #969966 . Please keep in mind that it is highly recommended that you keep related questions in one support thread or a forum post, so that we can easily keep track of your support history and provide better answers in a shorter time.
Also for convenience I included the answer to the current thread as well:
Please note that the recurrence ID / ID fields of the event is not part of the ISchedulerEvent interface to allow the user choose their type (e.g.: Guid, int, string etc.). The recurrence ID field is used to link expanded events to the recurrence head.
Also this field is required only in cases when recurring events will be showed in the widget and should be set to the same type as the event ID field.
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