Mine did that at around 5000 kms.
These cars have 'intelligent oil life' sensors, so the oil change notice will come up sooner depending on driving conditions, esp if you do short drives around town.
You can monitor oil lifecycle % in the settings menu, and you can also reset it if you're doing your own oil change.
I took mine to the dealer service for an oil change, was fairly inexpensive and quick.
Mine came up at 3600kms after her 3K service. Dealer showed me how to turn it off through (Steering wheel) Settings and scroll till you find it and reset it from there.
Full details are also on this thread http://www.mustang6g.com/forums/showthread.php?t=44770&page=4