r/netflix – Why not all episodes are 4k if it says ultra hd 4k ?

So, i'm watching netflix on PC. I watch through Microsoft Edge(only this browser can give 4k on netflix)I set the quality to maximum from settings and also my resolution is 4k, but on some tv shows some episodes are 4k and some are just 1080p. Example Better call Saul last season, first episodes are 4k and the last ones are not.

https://i.imgur.com/Bh8Lyfv.png