Measuring - with Finn and Bruno (Pixiv Fanbox)

[1 image - 4500x3600 px] Bruno notices Finn taking count of his length. Hm I think he's kinda cheating here. Alas, it's not the size that's important, but the way it's been used. And I believe Finn didn't use it correctly yet. How do you think, should he start using it? :)