Buffer capacity

My D800 can have 13 NEF (RAW) Lossless compressed 14-bit on the buffer (r 13).

On the D800_EN.pdf they say that 17 NEF (RAW) Lossless compressed 14-bit. (page 436) & thing go worse with JPEGs.

It must be because the card's speed, mine has 45MB/s and on manual they tested with an 80MB/s card, but I have doubts, the capacity is the capacity ... any thoughts?
Thanks.
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Un saludo.