The 10% service charge added - which is for the behind the scenes staff - and is shared among all the hourly paid employees.
There is a 10% GCT applied, which is a government tax and that is the government's take on the transaction - just like a sales tax at home.
Anything above the 20% (10% service charge + 10% GCT) is on you - and I would suggest if you want your server to get this tip - I would recommend you give it to them directly.
