I'm taking a list of values that are in the range of 1-20 and want to plot their average on a scale of 300-850. In other words, if all values are 20, the score should be 850. If all are 1, they should be 300. However, with my formula below, it's not working out exact. I'm bastardizing a formula I used in a different context with weights factored in so I'm likely off. Here's the formula where the list of values is in L2:L31

=(AVERAGE(L2:L31)
*(850-300)
/(1*20)-(1*1)
+300)

Thanks for your wisdom!