Thought this might be helpful for anyone else with the double SF/CP - this is from Nikon’s help center:
Do the following: keep the 2 buttons down until the word FOR starts blinking in the topdisplay. Release the buttoms and press both of them again a few seconds,
then the memory card has been formated.
This method is valid for all Nikon DSLR, provided that the camera has the 2 buttoms marked "Format".
If there is 2 memory cards in the camera, then it is only the memory card, which has been set to primary card, which will be formatted by using this method.
In this case the best solution is to format the memory card(s) via the menu.
unquote
This just for information.