I've just discovered that there are several versions of the Onramp course (R2018b, R2019a, and R2019b). The last two have slightly different presentation for the assignment (the first one doesn't seem to work properly) but in neither of them do I see that assignment under further practice. Which version are you using (look at the url)? Perhaps it is also language specific.
The assignment doesn't make sense and certainly won't be answered by the doc. You could rescale and recentre a normal distribution and possibly round it to integers but it still wouldn't be restricted to a range. And you could hardly call the result a normal distribution anymore.
You should report it as a bug to mathworks.