My H1B Visa extension was filed on 09/24/2015 when my visa was about to expire on 10/01/2015. That petition is in "Case Received" status and hasn't been approved yet. I would now like to file for a change of status to H4 as a dependent of my husband who is in H1B. In the form I-539, Question 12b asks for the expiration date of the current immigrant visa. What date should i specify as expiration date in this scenario?