What did the kids see Mr. Avery do one night off the porch?

In Chapter Six, the children witness Mr. Avery urinating off the side of his porch.

At first we saw nothing but a kudzu-covered front porch, but a closer inspection revealed an arc of water descending from the leaves and splashing in the yellow circle of the street light, some ten feet from source to earth, it seemed to us. Jem said Mr. Avery misfigured, Dill said he must drink a gallon a day, and the ensuing contest to determine relative distances and respective prowess only made me feel left out again, as I was untalented in this area.