600cc is a little more than a pint, which seems mighty small for a food bag. On ursack's web site the size of the TKO is listed as 650 cubic inches, which is quite a bit bigger (approximately sixteen times bigger, in fact).
I don't have one handy, but I'd suggest getting a 600 or 700 cubic inch stuff bag and seeing if you can fit what you'd pack for ten days into that bag. That will answer your question far better than I could. Better yet, you could experiment and tell us all how well it worked.
I'll assume that this is ten days and nine nights, right?
A couple of other suggestion for fitting ten days in a five-day sack come to mind, though:
The first day's lunch and dinner don't have to fit in the ursack. The other issue is that you are unlikely to replicate your initial packing job after your first day, so not having to fish food for the first day's lunch and dinner out of that superbly packed ursack and then repacking it will save you a lot of time and effort. By the second night the volume should be significantly reduced and repacking everything should be much easier. Try to put your next day's breakfast and lunch near the top for extra points.
Agressively repackage all of your food. This not only saves weight (and eliminates trash you'd have to pack out) it can eliminate a lot of volume.
Having lots of small packages (say one bag of oatmeal or cereal for each breakfast) will cause you to waste a lot of volume on packaging overhead. But having relatively few big bags will also be hard to pack efficiently. Try to shoot for a variety of container sizes. Having energy bars and the like loose in the bag is a great way to use up tiny bits of space that would otherwise be wasted.
Sizing your food to the bag: finding a brand of tortilla (for example) that closely fits in the interior of the container you use will be a lot more efficient. Having your bag or bear canister with you when you are shopping for food is a great idea.
More on repackaging: those 'eat-in-the-bag' containers and vacuum-packed bags popular for hiking meals (dinners in particular) are really bulky and awkward to pack compared to the same amount of food in a ziploc bag.
When doubling ziploc bags, I often like to use a thinner, cheaper, and less voluminous sandwich bag rather than a thicker, bulkier freezer or storage bag. Sometimes I just use two sandwich bags, sometimes I'll use one sandwich bag inside a freezerbag... although the lightest, cheapest, and least bulky bags of all are the poly bags you'll find in the produce section of your grocery store. You can (loosely!) tie them off and double them for secure storage of your food.
Consider bulk when you buy your food. Grape nuts are less bulky than granola or cheerios. Angel hair pasta is generally less bulky than ramen noodles. "Instant" foods are generally more bulky than their non-instant equivalents, even counting the additional fuel needed to cook the non-instant food.