Games with 2560×1440 resolution are too big for 2560×1440 monitor?

Hello everyone, I have a question.

I've already encountered the problem with F1 23 and Far Cry 5 : Although I could set the games to 2560×1440 pixel resolution, they were displayed much too large on my 2560×1440 pixel monitor. In other words, the games are displayed at the correct resolution so large on this monitor that the entire application doesn't fit on it, and about a third of the image is displayed on the other Full HD 75hz monitor. I'm absolutely certain that one monitor has a resolution of 2560×1440 pixels, so that can't be the problem.

Does anyone know the problem and can help me?

Thank you in advance!