The Tag you're reading of from the PLC should be an Analog Tag (0-3200 will be your range as mentioned).
Using this tag when create the bar graph or such, use it's scale function (0-100) which will take the reading of off your analog tag and scale it accordingly.
If you're reading a value of 16000 (50% of the analog tag) from the PLC, your bar graph will now display 50(50% of the scaled value)
PS: I forgot, the offset is not used here.