Line 2b is for the total of your dependents' modified AGI. If you do not have a dependent, or your dependent does not have modified AGI, you will enter 0. Your husband is not considered your dependent.
For more on modified AGI, see: https://goo.gl/rqyLyB
Form 8962, 2017: https://www.irs.gov/pub/irs-pdf/f8962.pdf
