For those of you playing along at home, the 1794-ID2 is a two-channel 24 VDC encoder input module for the FLEX I/O modular I/O system from Allen-Bradley. You can connect FLEX to many different network adapters, including the 1794-ADN DeviceNet adapter.
LSB, your problem statement is pretty vague: "My numbers are very inconsistent" doesn't tell us much.
Chapter 5 of the User Manual is dedicated to the mapping of the module data to a PLC scanner using DeviceNet.
What you need is configuration help, not programming help. Start by posting more information about your configuration of the module (and the rest of the DeviceNet system, like the scanner and the other FLEX modules) and maybe someone on the Forum can help.
My first question is: At 380 feet/minute, how many counts per second is the module getting from the encoder ? You will need to know the mechanical ratio from your conveyor to the encoder as well as the counts/rev value of the encoder.
That answer will help you calculate the Filter Constant setting for the module.