Nikon D6 Reference Manual page 259

A
The Memory Buffer
•
While the shutter-release button is pressed halfway, the frame-count
display will show the number of pictures that can be stored in the
memory buffer.
•
When the buffer is full, the display will show t00 and the frame rate will
drop.
•
The number shown is approximate. The actual number of photos that
can be stored in the memory buffer varies with camera settings and
shooting conditions.
•
Memory buffer capacity may drop briefly immediately after the camera
is turned on.
•
Memory buffer capacity can be viewed in the monitor during live view.
Choosing the Operation Performed When the Shutter Is Released (Release Mode)
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