It looks like floating point error. If I enter =(B3-D1) [note the parentheses that are needed to prevent Excel from arbitrarily deciding that this difference should be exactly 0] into a cell and format as scientific, I get 2E-9, indicating a very small difference between the two values.

Most of the time, floating point errors are handled using ROUND() functions. In your example, it appears that all numbers are integers, so perhaps rounding the values in column D to integers would be suitable =ROUND(currentformula,0) in D1 and D2.

The other solution might be to consider what the repeated division/reciprocal is supposed to be doing and try a different operation, since the floating point error is going to be introduced by the division/reciprocal operation.