Simplicity 5/14 chipper

Hi. Very automatively challenged here. I picked up a used chipper (model in title) to handle the debris in my yard. I think there is a solid chance it hasn’t been used in several years. I feel like an idiot posting this, but I can’t figure out how much oil I need to put in this thing. does not appear to be any gauge, and the cap does not have a dipstick. The manual also doesn’t say, that I can see. It just says “Oil level must be full. Do not overfill”.

Do I just measure what I remove, and then put in the same amount?

Thank you!