I agree with dchall san antonio above, trial and error is probably the best way to get to know your spreaders settings. I purchased a new Earthway 2170 last year and I spread milorganite, cracked corn, and alfalfa pellets purposefully, but also as a trial so to not do anything harmful to the lawn.

Then, when I applied a late season pre emergent I was more confident of the settings. I still had to stop and make small adjustments just based on a visible assessment of what the spreader was doing.

Lesco's recommended spreader settings are just an estimate and need adjusted. They listed Earthway spreaders on the Lesco pre emergent I had but I had to watch how it was being spread and then adjust up or down from there.

Edited to add: I just noticed this thread is over 9 years old. My apologies.