Spanish to English Bus/Financial Business/Commerce (general) Legal/Business

"CERTIFICA: Que en el domicilio social, con fecha X, el socio único, (Y) de esta sociedad acordó constituirse en Junta General de acccionistas, tomando la siguiente decisión: (he goes on to delegated powers)

Question: obviously, constituirse is to constitute (oneself,itself) but this use here is puzzling. Is it referring to a) the sole partner agreed to act in the capacity of the General Shareholders... (that is, he constitutes himself as the body or acts in its capacity) o b) agreed to convoke a General Shareholders Meeting... In the latter case, why not use convocar or celebrar? Hmmm.