The variable description page for POVERTY explains a key difference between the PUMS poverty values and those in IPUMS-USA. This excerpt from the variable description summarizes why your values are higher than those published by the Census Bureau:
“The original PUMS samples treated all households members unrelated to the head as one-person families when assigning poverty values, even if such persons were part of a secondary family (i.e., persons living with their own relatives but not related to the household head). Thus, the original PUMS poverty measure do not account for the presence of children (or any other aspect of family size and composition) in secondary families…Consequently, the original PUMS samples from 1990 onwards tend to underestimate poverty.”
What IPUMS-USA does in the variable POVERTY is evaluate poverty status for each distinct family unit in the household, as defined by FAMUNIT. This allows household members unrelated to the household head to belong to a secondary family. When the size of these secondary families expands beyond one, the poverty threshold increases, resulting in higher poverty rates.
I hope this helps.