As the time is divided into hours, minutes, seconds, milliseconds, … the zodiac is also divided into an hierarchical divisions. The initial level zodiac division is 12 parts each denoted as zodiac signs of 30°. For each zodiac sign, a planet is assigned as a sign lord. Except Sun and Moon, other seven planets get ownership of two zodiac signs. For example Mars is the sign lord of Aries and Scorpio. The astrological significant nine planets is taken into further levels of divisions. The entire zodiac is divided into 27 (9 x 3) divisions and it is called nakshatra divisions. Similar to the sign, each nakshatra has ownership lord which will be one of the nine planets, it is called as Star Lord. For example, Ketu is the star lord for Ashwini, Maga and Mula nakshatras. Further each nakshatra is divided into 9 parts as per Vimshottari Dasha period length and each part is owned by a planet which is called as Sub Lord. Again, Sub Lord portion is divided in a similar fashion into 9 parts denoting Sub-Sub Lord.
For better understanding, the following figure shows how the Aries sign is divided as star and sub lords. In similar fashion the other signs in the zodiac belt is divided.
Similar to the time accuracy like 11:30:34 145 (11 hour, 30 minutes, 34 seconds, 145 milliseconds), the astrological accuracy is done as Sign Lord, Star Lord, Sub Lord, Sub-Sub Lord for the given zodiac point. For example, the zodiac point 6° 50′ 53” can be astrologically represented as Mars (Aries – Sign Lord), Ketu (Ashwini – Star Lord), Rahu (Sub Lord), Venus (Sub-Sub Lord). This approach helps in distinguishing the twin births cases and other ambiguities in the astrological calculation.