Encoder Question

We are using an Absolute Gray Code Encoder that counts down from 255 to 0. I was wondering... we are upgrading from a Micrologix 1100 to controllogix and my question is how should I determine the starting point of the encoder? We are dropping out wet boards at a certain point in our lug chains and I am trying to determine based off the encoder value where that actually is in the lug chain spacing... hope this makes sense.

Can you use all zero as starting?

I am using Limit instructions with a given range depending on what I am needing to happen. I was thinking of basing it off where my first lug begins but so far that has not worked.... Using 0 isnt working either..