This is really important for me and you! For me, I'm notified that a student is coming in for help and that time has been set up for them. It also allows me to know what you need help with for when you come in the door so I'm ready to go and we don't lose vital work time together. And, finally, it allows me to find you or notify in case something comes up and I may not be available at the time you requested. If that happens, we will reschedule it so it's not lost time for you either. And for you, this makes you responsible for showing up rather than just saying "I'm coming in after school...".
(Note: The times are specific on the form, but they are a general time in reality. For instance, if one student signs up for 3 pm and one signs up for 3:15 pm, BOTH students can come in right at 3 pm for help. This was just the way I had to set up the form based on what the website would allow.)