screening distance of The Electrostatics Model

I have a case containing 40000 particles (radius: 0.3mm) and I use the Electrostatics Model.

When I set the screening distance to 5Rmin and 10Rmin respectively, the motion of the particles is significantly different, and the average electrostatic force of the particles is very different (about 3 times). 

Why is there such a big difference? Shouldn't particles that are far away have little effect on the electrostatic force received by this particular particle? Isn’t the screening distance of 5Rmin large enough? According to my understanding, the results of 5Rmin and 10Rmin should be very close.

I have read the introduction of EDEM2023 and the reference of the eletrostatics model, but I am still confused.