The restaurant must tell you if it wants to  make any use of your personal data beyond what is necessary or keep it for longer than is necessary for reserving your table (e.g. adding it to a marketing list).

They don't have to tell you they need it for reserving your table because (presumably) you already know that.

Article 13.4:

> Paragraphs 1, 2 and 3 shall not apply where and insofar as the data subject already has the information.