http://www.whitehouse.gov/blog/2013/04/12/president-obama-and-vice-president-biden-2012-tax-returns
"The President and First Lady also reported donating $150,034 – or about 24.6 percent of their adjusted gross income – to 33 different charities. "
soooo that's his chosen amount 150034 (13), a 24.6 (12), to their chosen 33 charities. Chosen rebellion (i.e. choosing to donate various amounts to various causes adding up to 33) bookending the 12 which was later calculated for them after the fact. Further, with the tax mess up in the air until this year they couldn't have backed into any of it if they tried.
In closing, the more science is "made available" & "learned" the more we'll appreciate how brilliant and divinely inspired the honourable David Flynn was while spending his time on Earth.