The three separate acreage amounts are .28, .20 and .17. The total of these three values is the total acreage under consideration.
You can add these values in Excel by typing a simple formula into cell B6.
Excel formulas always begin with an equal sign (=). Here's the formula typed into cell C6 to add .28, .20 and .17:
=.28+.20+.17
The plus sign (+) is a math operator that tells Excel to add the values.
If you wonder later on how you got this result, the formula is visible in the formula bar
near the top of the worksheet whenever you click in cell B6 again.