Question for tech person with good language skills

phendrick thought this was worth mentioning said

I’m having trouble interpreting this statement as to actual numbers.
From a Google developer page:

lossy WebP also supports transparency, typically providing 3× smaller file sizes compared to PNG

So if the “comparable PNG” file size is 120 kB, what would the “lossy WebP” size be?
Would it follow then that the PNG file is 3x larger? Or what?

Anybody know examples with actual numbers comparing the sizes?

I’m not familiar with using any image-editing applications, but might need to become such soon, so I don’t have background for this question.