Addition with negative numbers in a form

Hello, I am trying to add a column of positive and negative numbers on an electronically created form as shown below:

For some reason, the "Above Totals" field is treating the negative as a positive number, resulting in a total of 3 instead of 1. Once I finish typing in the next row; however, the field correctly treats the negative as a negative number as it should be calculated:

There seems to be some type of delay with this calculation that does not get corrected  until the user manually enters an additional piece of data. Is there a reason why this calculation is not happening automatically? Thanks so much.