How long is MGS 2? and does the game clock only count gameplay time?

My clock in the save menu says I've been playing for 2 hours, and I think I've been playing a lot longer. Not to mention, I beat the Tanker chapter and should be getting closer to the end, but Greg Kasavin of Gamespot said the game is 15 hours altogether. So, do I really have that much more to go? PS, much obliged if you'd tell me rather "Pliskin" is really Solid Snake or not.