The game zooms in when put in fullscreen in my 1366x768 monitor

Exactly as said in the title. These are screenshots of how the game looks when played on window mode at 640x360 resolution:


But, when played in fullscreen, the game locks itself at 1920x1080 resolution and proceeds to look like this:


Is there any fix for this? specially in naval maps, dealing with this zoom gets tiring. I'd love to at least be able to play at 1280x720 in fullscreen instead of being locked.