Right, exactly, it is absurd to think one man in a room with some symbols can generate understanding. But only because of scale, because we imagine a regular sized room, a normal sized book and a table with symbols on it. But it’s absurd because that system is incredibly simple, not due to any actual argument from fundamentals.
Who says the computer doesn't understand Chinese, though? In this case "the computer" is the system. The program, being the code, isn't a process. The man is acting as a mechanical piece of hardware. But the computer running the program is an active process with state.
I heard a lecture by Searle on this. He mentioned the idea that "the room understands Chinese" and simply dismissed it as absurd without considering it. This is exactly the problem with his argument. Well, that and the casual conflation of the man with the computer as if the CPU hardware is the system.