18 months rule?

[desperate_heart 0]

Hi Everybody, I was reading the Naturalization Guide at USCIS website and I read about 18 months rule about residency, I am married to US Citizen so before I apply for Citizenship shouldnt I leave the US at least 18 months? or they talk about an amount of total 18 months, I am confused, please someone explain this to me.

Thanks

[Boiler 45,567]

An applicant is eligible to file if, immediately preceding the filing of the application, he or she:

has resided continuously as a lawful permanent resident in the U.S. for at least 5 years prior to filing with no single absence from the United States of more than one year;

has been physically present in the United States for at least 30 months out of the previous five years (absences of more than six months but less than one year shall disrupt the applicant's continuity of residence unless the applicant can establish that he or she did not abandon his or her residence during such period)

has resided within a state or district for at least three months