what is the main camera size?

Im new in all this things of making videogames and i have a “problem” with the camera.
It works but doesn’t have any proportion with the canvas layers

in the editor it looks like this:

The preview looks like its wrong but then in play mode it looks just fine

how can i know the limits of the main camera?
for the main menu its ok because i don’t need to know too much about the limits but in the game have to know all the limits to distribute the space

Any help will be appreciated

Click on the Main Camera. in the Inspector there will be a list of options. One of them will be size. You can make the Camera larger or smaller when you modify that number. However, you have your Canvas set to Screen Space - Camera. This will ensure the canvas will fit perfectly in the Main Camera.