How do i match camera size/ game resolution to my tilemap?

Hello, I am completely new to Unity and game development as a whole and im a bit stuck on something here. I would like my game to have a fixed resolution of 400x240 pixels, and i was able to add a tilemap with 16x16 pixel tiles.
The problem arises when it try to set the camera to 400x240 pixels, as for some reason, my 16x16 tiles do not fit correctly within the bounds of the camera. I should be able to fit exactly 25 tiles in length and 15 in height (400/16 =25, 240/16=15), so my tiles and game resolution should be perfecty aligned, yet for some reason the tilemap just sits completely wrong in the camera. Even when changing the size of the camera, I cannot fit an exact number of tiles in the camera.
I have set the game resolution to 400x240 in project settings aswell. Fyi my camera also needs to be in a permanently fixed position.
Help would be greatly appreciated! :,)