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I was able to duplicate your result. I am assuming that your workbook is set to "Set precision as displayed". That means that if you show the Adjusted Percent with no decimals and Excel rounds those to just the 24, 60, and 17, Excel will add exactly those rounded numbers instead of considering that they were not originally exact. There are two options to correct it.
- Go to File>Options>Advanced and scroll down to When Calculating This Workbook. Uncheck the Set Precision as Displayed. Excel will then add the actual values including decimals even if not displayed, not the rounded values.
- Change the format for the percentages in Column B to show at least 2 decimal places. Even with the precision as displayed this will correct the issue in this instance. Since we are dealing with the question of rounding, however, it is still possible that there would be a particular combination that might still come up a point higher or lower.
Unchecking the Set Precision as Displayed is probably the best option unless you need it that way for other operations in the workbook. Then just make sure that there are sufficient decimal places showing in the Adjusted Percent to prevent it from creating an inaccurate calculation.