If the order was delivered on time, you have nothing to worry. Yes, once the buyer requests a revision, you will see the “LATE” notice, but it won’t affect your stats in anyway. Just work on the revision your buyer requested and deliver it when you’re done.
There’s no need for you to ask for an extension when being on revision. Extension is only to be requested if you feel you won’t be able to deliver the order on time (the delivery of the order, not the delivery of the revision).