There are no marks ‘added’ or ‘deducted’ for age as such.
What happens is that children of the same age (GL do it as born in the same month) are compared against each other. If there is a difference between, say children born in September and those born in August, then the scores are adjusted to take that into account. If there is no difference, then there is no need to adjust.
Theoretically, if the August borns did better than the September borns, then the adjustment woud go the other way!
This might help
https://www.elevenplusexams.co.uk/advic ... xplanation