All constant mass flow mCCRs (rEvo, KISS, COPIS Meg, etc.) work under the same principle, the O2 flow rate from the orifice depends on the IP pressure of the Ambient Pressure Regulator, higher IP = higher O2 flow.

Your metabolic O2 demand while diving a specific unit is determined by breathing on that unit at rest on the surface and watching what happens to the pO2. Once you have matched the flow rate to your metabolic O2 demand on that unit the need to add O2 is constant regardless if you are using a rEvo, KISS, COPIS, or any other mCCR.

For example if you have a unit with a low work of breathing and you set the O2 flow rate to .78 l/min and then were on a unit that had a higher WOB you might need to set the O2 flow rate to .82 l/min because the increased WOB will cause you to use more O2 at rest due to the higher level of exertion during respiration at rest.

Hope that clarifies things.
Rob