Taleo Onboarding - how to change due dates

Summary

Taleo Onboarding - changing the due dates and triggering an email on candidate start date

Content

Hi, 

How do i change the Duration (days) defined in the step (attached the screenshot). I am unable to edit the duration and also i could n't find out where the duration is updated.? if i change the duration, will that have an impact on the subsequent tasks?

Also how do i define a task which trigger on email on the candidate start date?

Thanks