To me this has always been the creation of an attack of magic darts, with each dart’s damage being evaluated by a single d4 i.e. scoring between 1 and 4, and adding an extra point of damage. One gets to roll a lot of dice.
A recent statement from WOTC is that one should roll one d4 and multiply that score by the number of darts, adding one for each dart.
The former rule, creates a tendency to an average of 10.5, while the latter rule evens out the probability of middling scores making the extremes of 6 and 15 more likely. Interestingly, the mean average remains the same.
Image Credit: by deepai.org