how some YT shorts fill more of my screen than others? arent all of them 9:18?

when i upload yt shorts its narrow compared to some yt shorts i see. i want mine to be bigger like this too. compare these 2 screenshots you can see bottom picture is narrower, why? i upload 9:16 videos on shorts but they are narrow like bottom one

https://preview.redd.it/j6w1cxma2s9h1.png?width=1184&format=png&auto=webp&s=0149e9012457249e62c388b63349bea3a816009d

https://preview.redd.it/6msuigle2s9h1.png?width=1013&format=png&auto=webp&s=238d190ca18e105cfd23ab82c7561d01e719b413