52.217-8 How Many Times Can Gov Extend Contract

52.217-8 Option to Extend Services states "The option provision may be exercised more than once, but the total extension of performance hereunder shall not exceed 6 months." Can the government exercise this clause more than once whereas the extension period lasts longer than six months? For example - Government exercised the 52.217-8 Clause for six months, but now at the end of the six month extension period they want to extend an additional three months, which would make the total extension period nine months. I'm thinking this is not allowed, but I'm not sure if I'm interpreting correctly.