Why doesn't Excel add these two cells correctly?

Without seeing the raw numbers and how they are formatted, it is difficult to say. I suspect that it has to do with rounding. If you can anonymize your file and upload a sample of data we can offer a better solution. It is difficult to determine what is happening in a picture. Offhand, and without further analysis I would suggest that you use the round function.

Attaching a sample workbook enables others to work on your problem:

To attach a sample workbook. Make sure there is just enough data to make it clear what is needed. Include BEFORE/AFTER sheets if needed to show the process you're trying to complete or automate. Remember to desensitize the data.

Click on GO ADVANCED and click "manage attachments" to open the upload window.


To add a file to a post