XanderGlasses will caption the person speaking the loudest and clearest near you.
In group conversations, people sometimes take turns speaking. In this case, the glasses will transcribe each person's voice.
However, if there are multiple conversations happening at the same time, then the glasses will pick up the voices from people speaking loudest and clearest — most likely that will be from the people who are closest to you. In the case of a restaurant, conversations from other tables are unlikely to be captured by the glasses.