Occasional part-day $ rate?

[Artsand crafts]

I usually have my appointments or my son's early in the morning. I open at 8AM and I'm usually back at 10 or 11 AM from the doctor's office. If the parent chooses not to bring the child I do not charge. If they drop them off when I'm back home (I call them on my way back) they pay the full fee. I usually remind them in advance by e-mail these 2 options.

[AmandaKDT]

My day is broken up into 0 to 4 hours and 4 to 10 hours. So if they are in my care longer than 4 hours they need to pay the full day rate.