Hand Held Spreader rate, one brand to another

I have two hand held fertilizer etc. spreaders, but neither is a brand that corresponds to the spreaders for which settings are listed on the bags of things to spread.
Is there some sort of comparison chart or formula that would allow me to confvert the drop setting listed on the bag with my own little spreaders?
I have: With settings:
Scott's Handy Green hand held spreader: Light to Heavy, twist knob
Frank's Nursery and Crafts no model name hand held spreader Numbers 1 to 6 on slide adjuster.
Meirman -- If emailing, please let me know whether or not you are posting the same letter. Change domain to erols.com, if necessary.
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