First, in answer to your question, you do add 19, but line 19 is the only line that you can control (i.e., this year versus next year). That is why I excluded it in the example to illustrate and magnify the opportunity. You can accelerate the timing of line 19...

An example to clarify your question. Add all three lines. Let's say they are $25 this year and $25 next year. So your total deduction for two years is $50. Instead, you accelerate $10K of tithing this year, so this year is now $35 and next year is $15, the same $50 total, but next year isn't $15, it is $24 (because that is the "free" money, the standard deduction). So this year is now $35 due to accelerating tithing and next year is $24 for a total of $59 instead of $50.

So, by accelerating tithing, you just changed from deducting $50K over two years to $59K, a $9K reduction in taxable income, which at a 33% marginal tax rate, is a $3,000 tax savings.

The reason I excluded line 19, was because if the other two lines total near $24K, there isn't much benefit in accelerating. Hope this makes sense.