I completely missed this feature from several months ago!
In Asana, when you have number custom fields in a project, you get a nice sum of values displayed at the bottom of columns. Did you know you can actually choose other functions to replace the sum, for example average, max, min, count? I did not, this was my latest discovery
To change the function, just click on the arrow next to the column header and click on “Change column function”.
And no you can’t customize the function (yet?).