So, I did answer that question ahead of time, but I don't think anyone really caught onto it, or I just wasn't clear. I don't know, but the answer is the same one I gave you in the IC:
"
The Masters in mind are pretty much like Ritsuka - freshman with unusual talent - however, you can be upperclassmen; so, juniors, sophomores, and seniors are the optimal choices for aesthetic.
Please, however, avoid being any kind of adult that wouldn't fit in CHALDEAS, if you don't wanna be a teen."
Admittedly, towards the end, I was so stunned, as they filled with prospects faster than I expected, so I prioritized accepting sheets on a basis that this question would return, and I could fill in the blanks with my original answer.
Day 1 is minimum of a month, to be specific there. None of you are actually starting your first day at school - which, do not get too hung up on that. It's a backdrop for downtime and presents more to do than traditional FGO. You won't be attending classes with a requirement to pass tests and whatnot, but you can attend classes as part of your scenes.
This particular universe is one that is ahead of FGO-Prime, but fell pray to hubris, and wound up in a similar situation of failure - minus the bombs.
@Yankee