The term Natal Lunar Phase Angle (Fertile Time) refers specifically to the angle between the sun and the moon when you were born.
When talking about or measuring Natal Lunar Phase angles, we remember that the moon travel in a circle around the sun (as all the planets do ). A circle is equal to 360 degrees. Therefore a natal lunar phase is a number between 0 degrees and 359 degrees 59 minutes.
For example, if a person is born on a new moon, when the sun and moon are said to be conjunct or together, the natal lunar angle is 0 degrees
Or if a person is born on the full moon, when the sun and moon are opposite each other the natal lunar angle will be 180 degrees. Refer to the diagram below.
The natal lunar is the angle between the sun and moon at any given point around that circle/orbit. It is a description of their relationship to each other and describes which phase the moon is at.
An individual has their particular natal lunar phase repeated when the moon is in the exact position relative to the sun as it was at their time of birth.
This position is not the same as the zodiacal sign that the moon was in at birth. To emphasise this point each month the new moon phase is in a different sign, so if you were looking at the moons sign and not its phase you would be making an error.
For example, if a person has a new moon natal phase, the natal phase is repeated whenever the moon is new regardless of the moons zodiacal or astrological sign.