It's funny, I originally had the idea to make this when I was watching a YouTube video on the Pomodoro Technique. I was trying to read this design book but was having a hard time focusing on it.
And one thing the person in the video said was to "[...] write down any distractions [during the Pomodoro session] on a piece of paper for later." - So I wouldn't forget this, I wrote the Pomodoro Technique's steps in the YouTube search bar (like I normally do when I need to remember something quickly) since it's persistent between pages. But since the YouTube search bar has a small size, I had to write the steps down simply, or else they'd be annoying to read later.
Then I had the idea to write a small note taking app that has a limited (64) character count. That way you're forced to write down your thoughts concisely; no "overly wording" things.
That was more of a design decision. 64 characters fit into a page nicely at 24px. 64 was just the highest round number I could use. It does make a nice note length though.