SUMIF after spreadsheet has potential error?

After completing the vlookup and sumif parts of the case study it was advised to change the "Net income" cells as the opposite to the sum used. In this case remove the "-", this can then be used as a check as the column total should equal zero. On the sheet I completed 2016 & 2017 worked ok, but 2018 did not sum to zero. After retracing my steps and getting the same outcome. I downloaded the "SUMIF_after.xlsm" file, and your version contained the same issue? 2018 did not sum to zero, but 2016 & 2017 did? Could this cause potential issues further in the case study?