Take GRE General Test once per calendar month?

I scheduled to take the computer-based GRE general test June 30th, and I also scheduled to take it again July 22nd, but I read on ETS website that the retake policy is "once per calendar month." Does this mean every 30 days (meaning I can't take it again July 22) or literally every calendar month (so retaking it July 22 is okay)?