Whoever set up the spreadsheet originally simply plugged in standard accounting formulas without performing any simplification. Gross Profit Margin is defined as the difference between revenue and cost of goods sold, divided by the revenue:

    GPM = (Revenue - CoGS)/Revenue

The equation in the spreadsheet you were looking at was looking at (effectively):

    (1 - GPM)\*100

True, it could have been simplified, but there are (at times) reasons for not performing every possible simplification. In this case, to someone who "thinks" in terms of CoGS, Revenue, Margins, etc. the equation given makes a lot of sense. To a programmer (or a mathmatician) it is not very efficient, but to the accountant it provides self-documenting code. This is especially important in Excel, where you can't add comments to the code (cell equation). It appears that they were trying to calculate the proportion of each dollar of revenue that the company spent as expenses.