I'd ditch that pack capacity table. It totally depends on the bulk of your other gear, which is why everyone recommends (or should recommend) that the pack should be the last gear purchase. I can go for 10 days with a 40 liter pack (plus outside pockets). As Gershon says, a pack with your gear inside carries quite differently than a pack with sandbags, particularly if you don't have the rest of your gear and therefore have no idea of the weight and bulk that need to go inside.

The only way you'd need a pack as big as the one you recommend for 5+ days is if you're packing a big herky synthetic fill sleeping bag designed for winter temperatures. Or for a parent sherpa-ing for small children. Or my youngest son hauling a bulky, heavy wet suit to surf on the Olympic wilderness coast.