Earlier quoted context omitted.
I (and probably the vast majority of people) don't have to do any calculations to know I'll have less than $24,000 in deductions because $24,000 is ridiculously high amount.
You can deduct state taxes which adds up. Really 24,000$ is easier to hit than you might think.
My deductions were usually only around ~$17,000 with pretty decent charitable contributions, I don't even have to think about if I'm going to itemized this year. I suspect I'm a pretty "average" itemizer.