1 = Center of the earth
2 = History, Makkah during Abraham.
3 = Year 157 before Hejrah, Makkah during Gussei, Grandfather to Prophet Mohammed.
4 = Year 12 before Hejrah, Makkah during Guraish.
5 = Year 91 Hejrah, Makkah the Omayied Era.
6 = Year 310 Hejrah, Makkah during the Abbasied Era.
7 = Year 1215 Hejra, Makkah during the Ottoman Empire.
8 = Year 1412 hejrah, makkah after completed by the Custodian of the Two Holy Mosque, King Fahd bin Abdul-Aziz
source:http://www.anwary-islam.com/kabah.htm