I don't see why you'd think anything was wrong with that. I even did the math now and agree with your specific value of £125. Your value of 0 is correct in the other case too. About the only thing I don't agree with is your sense of surprise. There's plenty of information that's worth nothing, and no reason it couldn't later be worth something in combination with other information.

For example, if he told you the d12 numbers were written in red pen (and the others in blue), that's worth nothing on its own. But suddenly looking at one of the numbers is worth quite a lot more than it was...