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The AFM60 is a SICK family part number, which is good. SICK is one of the industry leaders in absolute encoders, especially ones that use the EtherNet/IP protocol. To my knowledge, some of the EtherNet/IP encoders that Rockwell sells are SICK hardware.
Are you using a generic EtherNet/IP Module object in a ControlLogix (are you using ControlLogix ?) or an "Add On Profile" ?
In general, the relationship between counts and revolutions is either programmable or part of the part number. My experience with SICK is that the number of counts/rev is often part of the part number.
Those AFM60 family are likely more programmable rather than preset to a specific number of counts/revolution. The maximum resolution is 18 bit x 12 bit (262,144 counts/revolution x 4,096 revolutions for a multi-turn encoder).
The actual distance that your mechanism travels in revolutions or inches or millimeters is dependent on your mechanism. You need to closely examine the wheel or gear or pulley or screw that the encoder is attached to.
I always draw up a simplified cartoon of the powertrain and the encoder when I'm programming and configuring devices like this: even after decades in the industry it's important to double-check and make sure you've accounted properly for all the ratios and scaling in your machine.