I was thinking we are all getting peed of waiting for EAD's but if you have a Interim lets say? and it expires surely if you are working then the Employer is not going to let you go knowing that you have applied and already had a Temp one?
Also when you get an Interim that allows you to get your S/S which is what you are really looking at or rather what the employer wants............
So can't we just apply for another Interim EAD if you so wanted too? personally I would not bother if I was already employed and had the S/S.
Just a thought

Did you said you got a interim EAD on 91st day from the receipt date( not from notice date)? I hope that's the case.

How does the INS officer calculate it?

Yes it was the RECEIPT DATE for sure I was dated 6th Feb and got my Interim May6th.

Well there was a tray with Interim EAD sitting there I filled my form out specifing why I was there? and they called me? they must already have the dates set up at the start of each work= day, ie they knew that any Interims where effective the day I went from the 6th Feb and so forth.