Letter For Service Hours Completed How Long Should I Wait To Ask For A Recommendation Letter/reference If I'm Volunteering?

How long should i wait to ask for a recommendation letter/reference if I'm volunteering? - letter for service hours completed

Hello, I have about 25 hours of community service in a struggle of a certain time each month. I volunteer in a school. I must say that working with children as my research assistant, I will go. But I want to leave if I am 40, 50 hours of community service. How many hours of community service is recommended before requesting a letter of recommendation result, monitoring and supervision? Thank you.