I didn't do my homework well in advance. I went too early on the first day and didn't see it. I arrived at 9:10 p.m. the next day. I only watched it for 10 minutes. I thought it would spray again. I waited half an hour until I knew that 20 minutes of spraying would end from 9:00 to 9:20 p.m. every day. But it's shocking to watch it for only ten minutes!