Here's the bottom line. That charger is going to shut itself off, completely, when the battery gets to a certain voltage. You have no control over that, other than to sit back and watch it (the 2 red lights go to one red and one green when done).
RAD's thinking is that this charge cycle may not fully charge ALL of the cells in a NEW battery pack. Some cells, which may be a little low, may not get enough charge during a standard charge cycle. This in mind, they supply the advice they've given.
You can ride it a couple of miles, then charge it, without issue. Won't hurt a thing. You can do that a couple of times that day. When you get done messing with it for the day, then plug it in and leave it for 12 hours, and maybe do the same thing the next day after a short ride. That should do it.
"Best practices" for max battery life will tell you NOT to let a battery sit when fully charged. A few hours sitting prior to use hard to avoid on occasion. What you would want to avoid is letting it set for a couple of weeks fully charged.
Many consider ALL of the above overthinking the subject and just charge/ride as they wish. The battery is still going to last for years....