I am a CM seater at Sanaa. While you can come up to 20 minutes late and still be seated, if you are much later, we will most likely be able to accommodate you, but you definitely might have to wait a decent chunk of time (up to an hour) to get seated if we are really busy. So I wouldn't book it intending to be late.
Also pay attention to the hours of the restaurant. For instance, we close at 3. The last ressie is 2:55. If you come after 3:15, our kitchen is closed until 5 and you would not be able to order the full menu, only the three things we serve in our lounge while we are "closed".