You can also do a mock-up of sorts by buying one can & trim, and get something to serve as a shelf of about the same depth, perch the 'shelf' on something (boxes?)against the wall a couple of feet above the floor, hold the can light a couple of feet above that and move it back and forth to see what distance makes the best overall light coverage at the 'shelf'. A little trial & error without any damage and little cost.
There are 10 types of people. Those who know binary, and those who don't.