I have much more coef 5 items than 1/2000 and far less than 1/3*C53 chances in 2000Did you misread it or are you saying you have less than 3/2000 coef 5 items in that last part of that sentence? I don't understand what you meant by it. Perhaps if you compare what you have to the percentage instead it would be closer? (3/2000 is slightly bigger than 0.14%).
Also, don't forget that its just approximate, especially when it comes to the coef 6 items. You also need to consider if the difference could just be an effect of randomness.
If I understand correctly, the person gathering data took numbers from several people, but wouldn't accept it if they had less than 10,000 items, but some were a lot higher than that; rollerfou having 80,000 items was mentioned. I don't think the fact that not all items appear when you first play was taken into account which may alter the results slightly, but only accepting info with 10,000 items or more would decrease that effect. I think that the coef 5 value isn't far off at least. I can't be sure about how accurate the value for coef 6 is without knowing more about how many items were contributed in total.
If you want to see where I got this from, take a look
here.