H1B petition expiring on 02/7/17. Extension applied on 12/28/16 (premium mode) but no receipt# or status update


My H1b petition is expiring on 7 feb 2017. H1B extention + amendment request is filed on 28Dec 2016 in premium mode. But I still did not got receipt# itself, obviously no update on status

In worst case, if I dont get any update till 7 Feb 2017 should I leave US or I can stay for the grace period of 240 days as I have already applied for extension even though I didnt received receipt# ?

Thanks in advance

Srikanth Puvvada