How do you want to handle any device conflicts? That is, what should happen if (based on your matching criteria) that Directory Sync Pro for Active Directory finds a matching device already in the target? If you choose skip, Directory Sync Pro for Active Directory will not make an association between those devices, and an error will be noted in the log file.
If you choose Update, Directory Sync Pro for Active Directory will consider those items the same. This means that any changes to the source device object attributes will be made to the target device, if you have allowed updates to occur. No new object will be created.
With Rename, a new Active Directory device object will be created in the target. You will need to distinguish this from the matched target object by giving it a new name. You can manually add a prefix or suffix of your choice, as long as it does not exceed 20 characters, or, you choose any existing AD attribute to be prepended or appended to the name. Remember that if you choose rename, when you update the device object's attributes in the source, it will be the Renamed device object in the target that gets updated during a synchronization.