I think this is the answer to my "concern". As the light green curve (quantized calculated curve) is quantized to 3m by design (something I didn't know), it appears like it has been set to have a last stop at 3m (instead of the 6m that the DC is set).or quantized to 3m/10ft.
Learning something new every day...
Of course all these have nothing to do with real on/off-gassing as they are post dive and for illustration purposes only.
Thanks for clarifying