Govt runs $44 billion surplus in December; Natl Dept up $135 billion

Revenues are up 5% over December 2012 and outlays are down 10%.
See http://www.cbo.gov/publication/44999.

So this means the national debt dropped in December, right?  Wrong.  The total national debt was $17.217 trillion on 11/30/13 and $17.352 trillion on 12/31/13.  How is this possible?  Some sort of trickery, smoke and mirrors.

Update:  The national debt jumped $125 billion on Dec. 31 from the 30th.  So that's a big part of it.  But why did it jump? Intragovernmental holdings, as part of this 1 day increase, jumped by $79 billion.  But why?  Doesn't that money represent tax money that came in from Social Security or related trust funds that was spent by the general fund?  So how was it spent if there is a surplus?

The Daily Treasury Report for 12/31 shows Cash on deposit with the Fed of $162 billion vs. $33 billion at the beginning of the month.  That's a $129 bn increase.  But we are still missing about $50 bn or so.  The cash increased by $95 bn on 12/31 but the national debt increased by $125 bn on that date.  That's a $30 bn difference. What happened?  Did Moochelle go on a shopping spree? (joke)