GF99 or equivalent function on 2N

[Markus MDDT]

Hi Guys!
Im trying to understand if there is a function for seeing when you start off-gasing and how "well"?
I think I should be able to use the graph but I dont understand it and I am not able to find any tutorial. Do you have any info?
I am also wondering about Customs function 08. Is this possible to setup as a GF99?

My dives are usually normoxic trimix, CC scootering but we do prehaps 20-30 min on bottom but we dont go to our ceiling to decompress after that, we scooter around and it would be very good to have the off-gasing threshold at a glance on the OSTC 2N instead of pushing the buttons on the sherwater 10 times.

Thanks