Hi. I have downloaded the .csv file and when filtered the values based on CustomerID = 17850, I have found out there are negative units in quantity. I have not understood what that is..!! but if we observe the histogram, we see there is no exact 0 point on x-axis. and also we can see that histogram is extended from -30 to 70 on x-axis horizontally and frequency on y-axis is times of quantity that customer brought number of times.
Like quantity of 10 to 20, he brought more than 80 times.