Nobody said "quarter" means multiply by 4. They said "quater" means multiply by 4, which it essentially does [1]. In addition to being a real word, it's also a prefix, e.g. "quaternary" means fourth in order.

You made a typo (quater) in correcting someone's else's typo (forth). Several people have pointed out the irony and have patiently tried to teach you a new word, but you seem to keep reading past all of them without comprehending ¯\_(ツ)_/¯

[1] https://www.dictionary.com/browse/quater