Also, a surprising number of people don't know that precentages are more often than not represented as decimals between 0 and 1 as opposed to actually a number out of 100 when used in calculations (because the concept of a percent doesn't really exist in math, it's just a context specific way of formatting a decimal). A lot of people just enter 69 when calculating a formula that operates on a precentage instead of 0.69 which obviously makes the formula useless, or if a formula is supposed to output a precentage, they assume that it output 0.69 percent instead of 69 percent.