Difference in the numbers when creating same metric in a different way

I have two metric just built in different way. (Value 2 and Value 3 are unique events for a specific page type, it could be used with the segment A which is a page type or without. 

1) (Segment A: Value1) / ((Segment A: Value 2) - Value 3) : does not match Manual Calculation

2) (Segment A: Value1) / (Value2 - Value3) : Matched Manual Calculation 

When I break down the metric, that absolute numbers match for both the calculations.

Any thoughts why would this be?