erm....well quite a lot to be honest. and I mean, A LOT. Don't go overboard with it, just drink to when you start to feel confident/in a good state, then I would stop there if I was you.
That said, don't worry if you keep on drinking from there. It depends on what you're drinking, but if you drank about 35cl of vodka, you'd be completely trashed most likely, but you wouldn't have situations with your liver stopping or you needing hospital or anything. It's hard to say how much you can drink before that happens as it varies person to person, but generally you would need to drink SO SO MUCH for that to happen. If in doubt, just don't drink, there's no pressure to.