What's happening is an inherent limitation in IEEE Double Precision
Floating Point math (which nearly all spreadsheets use):

http://cpearson.com/excel/rounding.htm


To prevent it, you can use explicit rounding:

=ROUND(1282.4-1282.39,2)

or you can use the global Tools/Options/Calculation/Precision as
Displayed, which will truncate all your values to what is displayed.

In article ,
Mike A <Mike wrote:

In Excel if I subtract, for example, 1282.39 from 1282.40, and the answer
cell is displayed with 14 or more decimal places, the result displays as
0.00999999999999, when in fact the correct result, obviously, is exactly
0.01. What's happening here, and how do I prevent it?