spot on Ozstache, beat me to it. calculated daily, compounded monthly is the problem.

As a completely irrelevant aside, if you continuously compound (that nebulous impossible concept beyond daily, hourly, per minute, per second, per yottasecond), the growth factor you get is Euler's exponent.

E.g. $10000 continuously compounded at 5% interest rate grows to $10,000 x e^.05 = $10,512.71

If that $10,000 was compounded once per year obviously you only get $10,500. So the extra benefit to compounding over shorter time periods is limited to $12.71 in this instance.