Regarding Start Date,Plan Date & Call Date

Dear SAP Folks,

I created a Strategy based maintenance Plan in which the call horizon is 100% and scheduling period is 7 Days.If I enter start of cycle 30.06.2015 and scheduling using IP10 it gives eight scheduling list while I scheduled for 7 days.If I enter the start date 01.07.2015 it gives seven scheduling list that is correct.

So I am unable to understand the concept of start date plan date and call date and is it possible to schedule the plan in past date?

Thanks

Regards

Gaurav