That is saying that, in the equation, there is only a 10% chance she will give birth, how ever often the equation calculates.
Other things of note:
<Dynasty_TurnAgeGrown>100</Dynasty_TurnAgeGrown> Before your kids can do anything
<Dynasty_MinTurnsBetweenChildren>20</Dynasty_MinTurnsBetweenChildren> Before she can have another
<Dynasty_MinTurnsUntilMarriage>50</Dynasty_MinTurnsUntilMarriage> Before kids can marry to another faction
<Dynasty_ChanceToChangeAllegiance>0.67</Dynasty_ChanceToChangeAllegiance> The chance yours or AI kids will defect