The 350ml is the oil volume for the outer chamber. People sometimes use a lower volume depending on their set-up and preference.
You will also need to add oil to the inner chamber. I do not typically measure the oil in the inner chamber as any excess oil is forced out of the cartridge when bleeding the air. I believe the volume is somewhere in the 200-220 ml range, but the manual should tell you.
Here are two videos that I have found useful:
https://www.bing.com/videos/search?q...9&&FORM=VRDGAR
https://www.bing.com/videos/search?q...6&&FORM=VRDGAR