I’m hoping it’s just a visual display glitch saying that there’s 37/30 people in the guild, but in fact the correct number of 30 players are present.
The bug where it’s displaying 30/30, but you actually have <30, is a much worse bug because not only you can’t invite any new members, your guild won’t appear in the in-game Guild Recruiting lists either.
Edit: Sirrian made further mention of this issue over here