H1 B ext. approved and expired before approval

[Pinky88]

My h1 B extension was applied in November 2017.It is approved on April 11 2018 after an RFE,i received the copy of approval on april 17, 2018 but the expiry date is march 2018. My i94 is also expired. An extension should be applied 45 days before i-94 expires. In my case i was informed a week 17 days after it got expired. Could this be a typo graphical error, or is this how H1 B extensions are being approved these days. As per my knowledge Earlier it was a minimum of one year but i got it approved for 3.5 months now and it expired even before i received it. What is the best thing to do now? I have already submitted a service request for typographical error on uscis site. Should my employer file for an extension now? How long can i stay in usa now, since i am aware of my i-94 expiral only after 2 weeks after it is expired.