Thanks for those photos !
The Fest CPX-FB36 is their 2-port EtherNet/IP adapter for the CPX I/O and valve manifold system. The data maps can be very complex because CPX is so flexible with the variety of I/O modules, regulators, and valves that can be assembled and connected.
Even though my company uses these extensively, I always have to poke values into the I/O tags to help myself correlate the tag addresses with the actual valves.
Because this is a system that's already working, you can use the existing program and configurations and improve their documentation and comments.
First, figure out the IP address of that CPX-FB36 adapter. Maybe it's labeled on the cable, or in a drawing, or you know which one of the objects in your Studio 5000 project I/O tree matches it.
Open up that IP address in a Web browser and take some notes about the configuration and modules that are displayed there.
And download the Festo Maintenance Tool (FMT) from the Festo support portal. It will allow your computer to connect and upload the configuration of the module and allow you some access and monitoring in addition to what's in the Web Browser interface.
With just two outputs on in the Output tag associated with the Generic Ethernet Module in Studio 5000 for that CPX-FB36, you should be able to figure out which of the bits in the Output
ata[x].y tag are associated with which valved. Generally bits 0,1 are that first valve, bits 2,3 are the second valve, and so on.