David,
Either of the two configurations below are acceptable. The second one is more of a configuration used if you are using the RO water for drinking water. The drinking water would be taken from after the second carbon filter (placed there for taste):
> water in
> sediment
> carbon
> carbon
> RO membrane
> DI Resin
> DI Resin
> water out
OR
> water in
> sediment
> carbon
> RO membrane
> carbon
> DI Resin
> DI Resin
> water out
If your setup is not like either of the above, we will need to follow up with AquaFX tomorrow. Can you take a picture of the setup for us?