From http://voices.yahoo.com/how-report-amounts-form-1099-div-2439-11819489.html, I learned that
Specified private activity bond interest dividends reported in box 11 of 1099-DIV is the portion of tax-exempt interest dividends reported in Box 10 that may be subject to an Alternative Minimum Tax (AMT).
They are included in the alternative minimum tax calculation on Form 6251 if you are subject to that tax.
I wonder how to know if I am subject to AMT, and therefore need to include specified private activity bond interest dividends in Form 6251?
Btw, my Specified Private Activity Bond Interest Dividends is $0.51.