That's the accumulative total of bows during the sixth graders' graduation ceremony, for everyone in the hall. Even to get their certificate, each one of the 66 students had to bow seven times between standing up and returning to their chairs.
Of course, they've been practising for weeks; not just them, but the lower grades as well. They sang several songs - there are a lot of graduation songs to choose from in Japan - and they sang very nicely. I think three of the students actually played the piano for the graduation songs, and very well. And when they all stood on stage and recited memories of their school life and whatnot - one boy would say a sentence, then another, then a girl, then all of them. (Hey, they even mentioned me...). The lower grades also had things in the script to say, too.
So, a very formal affair, and it was de rigeur for the parents to wear black clothes. The sixth graders wore their new uniforms for junior high school, which they start in just over three weeks. Most of them are going to the same school, joining students I taught at other elementary schools. Two or three wore different uniforms.