Changing the proposed start date to be earlier

Summary

Changing the proposed start date to be earlier

Content

Once we create a pending worker from "Add Pending worker" from the UI with a proposed start date in the future. The Effective start date of the PW assignment and the proposed start date of the employee record are same. In this case, how do we change the proposed start to be earlier than the date entered while creating the pending worker. The system wouldnt allow to select a date earlier than the PW assignment start date. 

Any thoughts on how this is achieved from the UI?

Version

19C