At the start of pregnancy its kinetic is the most important factor.
600 is usually at the start of pregnancy. Between 4 to 6 weeks of amenorrhea.
The exact datation of pregnancy will be done using your last menstrual period date and the ultrasound of the first trimester.
the age of pregnancy will be related to the date of last menstrual period which will be calculated by your doctor and confirmed by the obstetrical ultrasound.
the level of 600 0f bHCG meaning that the pregnancy is just in the first week approximately 4-5 weeks. we need to check it again to confirm that the level is double in 48 hours after the first test which will reassure us that the pregnancy is viable in the uterus