Does anyone know what the total 2 stroke oil capacity is on one of these?

I thought my bike was eating oil as it dropped to bottom of the see through hose (which I thought inferred it was near empty) after very little mileage and was panicking but I now believe it's more of an indicator of how full it is rather than how empty.

Today I was probably about 1cm from the bottom and filled it up and it only took about 100ml of oil and I'd probably done about 30 / 40 miles since I last filled it.

I'm just trying to work out a conservative mileage I can get from full to empty against how many miles I've done and how often I've filled up with petrol so I'm not running (read killing) it without any 2 stroke.