Also- I think it would be kinda bad to see the numbers if you got fixated on them.. seeing your friends or families numbers drop, wondering what you did that day that they didnt like, getting hung up on getting them to go up etc etc - but I think you'd want to ignore that kinda stuff if you made a cute manga series of this idea.
Yeah, yuri doesn't need to go all Black Mirror .-.
...I'm a bit against everybody calling the MC "dense". She's just uninformed (on that particular symbol). She has one reference to the symbol, though, and while it leads her to the wrong one, it gives her a - to her - satisfying conclusion (a buggy 8) that negates her need to do further research.
Her ability is a mystery, to herself as well it seems; she may be used to figuring things out on her own (like the scaling system).
The fact she never came across the infinity symbol any other way, depends on the japanese schooling system and her interest in educating herself beyond school / what hobbies she has / had or even parental influences.
Either way, I would like this premise as a full series. Not sure it would work on this chapter, though... but might as well .-.
It was short, but entertaining to read :)