In  mode, the display on  the upper left of the screen shows the SD card icons and the remaining recording time* (in minutes) on each card.

On the [Media] status screen, you can check the total space, used space, approximate remaining recording time* and speed class of each card.  For SD card B only, the approximate remaining number of photos will be displayed as well.

* Remaining recording times are approximate and calculated based on the current video configuration used