I'm struggling to understand the CDF for the discrete uniform distribution (line 1 of the first page). I think the equation is missing a "+1" in the denominato

I'm struggling to understand the CDF for the discrete uniform distribution (line 1 of the first page). I think the equation is missing a "+1" in the denominator as otherwise it doesn't make sense. Although it has been a while since I took a stats class, so I may be mistaken