If you're trying to figure out how high up to place the Hovr Slim in your shelf, have no fear, you've come to the right place.
In general, you will be using the Slim for shelves thinner than 2" and as thin as around 1.5". That means you won't have an enormous range of options here, but in general, your best bet for placing the bracket channel in the back of the shelf is to cut the channel so that the top of the bracket is 1/4" from the top of the shelf. This should leave you a bit of space below in most installs to conceal the bracket from the underside as well, while not leaving it too far one way or the other.
There are niche scenarios in which you might put the bracket 1/8" from the top of the shelf as well, however this will generally be when you are installing into a very thin shelf where you are leaving minimal shelf material above and below to fit the bracket. Generally we recommend against this as it becomes very easy to accidently blow out an edge and waste a good (and expensive) piece of wood when cutting the channel with margins this tight.