請教8老師: EAD card

My husband filed EAD this April with receipt number starting with MSC(got card less than 2 month); mine filed in Sep with receipt number starting with LIN(not yet get card almost 3 month).

And both our 485 starting with LIN. we lived in Chicago and never changed address.

My question is that normal? which is correct? how come they are different office? Please advise.

is matter how soon to get EAD approval? thanks a lot