Auto Repeat for Sales Invoice

Can anyone please explain me how Auto Repeat scheduler works?
And how next schedule date is calculated according to given frequency?

Hope to get reply soon…
Thanks in advance

Check this out:

Updated for V12

Thanks @rmehta,

My scheduler is working on time now, but I want to add ‘service start date’ field and ‘service end date’ field, in ‘Auto repeat’ form,
and change the dates according to ‘new schedule date’.
Now I am not getting, where and how to do this, please help me if you understood my problem. I am new to ERPNext.

Thanks in Advance.