The definition of '100m'

I'm feeling rather short-changed at the moment.

There is just no way that my last ball of Noro Silk Garden is '100m', as the label says. I know that the label yardage is just an estimate but surely.. there cannot be anything more than 50m in that last skein.. unless the length of every bit of twig and hay is also meant to be added to the yardage? Hmmm...

I was very careful to take note of my yardage at the beginning, so I am absolutely sure that I used up exactly 1 ball (or 100m) to knit from the beginning up to the entire increase section. According to the pattern, the decrease section is basically a mirror-image of the increase section, right? Therefore, it should also take 1 ball (or 100m... see I'm smart) to complete the decrease section. But it sure doesnt look that way at all!!

When I'm done sitting here snarling at the little pouf of yarn left, I shall have to make a decision to either rip back & make the scarf even shorter, or buy another ball of yarn online. Snarrrl.