The LD 50 of allium sativum is estimated to be somewhere around 3034 mg per kg for rabbits and something similar in mice. So your upper limit may vary as a human. Source.
I’ve eaten quite a bit. I found a boundary when I ate garlic that was a bit older and starting to root… that hurt badly. I still don’t know the boundary in terms of amount, but I make sure my garlic is very fresh.
You can put slithers of garlic in your socks & when you can breathe the garlic on your breath you know it’s worked its way through your body. This way you get all the benefits of garlic & it won’t upset your stomach as garlic I’d a greasy food that gives a lot of people gas & stomach upsets.