Looks like it came from the same people who write the tax codes.

‘‘(ii) AMOUNT.—Subject to clauses (iii) through (v),
the applicable amount specified in this subparagraph
for an eligible professional is as follows:
‘‘(I) For the first payment year for such professional,
$15,000 (or, if the first payment year for
such eligible professional is 2011 or 2012, $18,000).
‘‘(II) For the second payment year for such
professional, $12,000.
‘‘(III) For the third payment year for such
professional, $8,000.
‘‘(IV) For the fourth payment year for such
professional, $4,000.
‘‘(V) For the fifth payment year for such professional,
$2,000.
‘‘(VI) For any succeeding payment year for
such professional, $0.
‘‘(iii) PHASE DOWN FOR ELIGIBLE PROFESSIONALS
FIRST ADOPTING EHR AFTER 2013.—If the first payment
year for an eligible professional is after 2013, then
the amount specified in this subparagraph for a payment year for such professional is the same as the
amount specified in clause (ii) for such payment year
for an eligible professional whose first payment year
is 2013.

That cleared it up for me.  You?