Population of US states in 1880 full-count census different from official numbers

I downloaded the 1880 full-count census of the U.S. from IPUMS. I tried to compute the population of each state to check consistency, but the numbers are different from official figures. For example, the Census Bureau counts 622,700 persons in Connecticut, whereas I find 623,548. The numbers are similar, but is there a reason for this difference? Thanks!

These small differences between the 1880 complete count database and the original published tables are to be expected. There are many sources of such divergences, such as errors in the original tabulations, information in original tabulations that was not in the census sheets, missing data, and the cleaning up of duplicate records.

I hope this helps.