How do I make sure the streamed movie is in 4K.

I have a very fast Internet connection, a 4K 60HZ Samsung monitor.

When I play 4K video from YouTube, I can check it by click setting icon, also from setting icon, it has a little red 4k showing the video being played in 4K.

Now, I purchased a movie Free Solo, it doesn't seems played in 4K.

How do I sure the movie is played in 4K is my question. I'm not playing it on TV, I have a MAC mini, using Apple TV video App play on connected 4K monitor.

Thank you.