Numbers are in part about tables and in part about fire code and maximum number of persons allowed in the building. In a very popular restaurant like BoG it's not always easy to add a guest. And I know others have mentioned there are smaller tables that fit 2 or 3 in some restaurants so that may be an issue.
You could attempt to make an ADR for one for the same time. I know others have done this for breakfast and then they have been able to find a table together. I've yet to see all tables filled at BoG during lunch so I would think it might be doable, but perhaps not ideal.