Retainer fees and playgroup attendance - can anyone clarify the NCMA contract for me?

[chickenmama]

I have agreed with parents that a half fee will be payable during the 6 hrs their children are at nursery. I have noticed that sometimes people call this a retainer fee, but looking at note 6 on the back of the contract it doesn't really fit and it seems to be contradicted by note 24 on playgroup attendance.

Can anyone clafify for me?

I include payment under normal charges eg daily £15 but under additional notes for contracted hours clearly state times days child will be at nursery and that those hours are included in daily rate at 50% hope this helps