It's a bunch of gibberish, but here is the new section of the law:

‘‘(3) INCREASE IN CREDIT AND PHASEOUT PERCENTAGES.—The table contained in subsection (b)(1) shall be applied by substituting ‘15.3’ for ‘7.65’ each place it appears therein.

‘‘(4) INCREASE IN EARNED INCOME AND PHASEOUT AMOUNTS.—
‘‘(A) IN GENERAL.—The table contained in
subsection (b)(2)(A) shall be applied—
‘‘(i) by substituting ‘$9,820’ for ‘$4,220’, and
‘‘(ii) by substituting ‘$11,610’ for ‘$5,280’.

In a nutshell, you get a 15.3% credit if your income is up to $9820, it stays at that amount until $11,610, then it starts phasing down after that.

It is fairly simple calculation for a single person with no kids (well, after you decipher what the legal gibberish means), but the numbers/calculations aren't quite as easy with kids.