Check the config.ini file that should have been included in the folder you exported the game into. See if it contains a line that says FULLSCREEN = YES, if it does then replace yes with - it's not case sensitive. If it doesn't contain that line then add it. You also need to add a line that says RESOLUTION = 1280x1024.
By the way, that's a strange resolution you are working in. Why did you decide to use that one? The most common monitor display resolution is 1920x1080 & in general any resolution that uses an aspect ratio of 16:9. 1280x720 (720p), 1366x768, 1600x900, 1920x1080 (1080p), 2560x1440 (2k), 3840x2160 (4k).
I would say 1366x768 (laptop) & 1920x1080 (pc) are the most common resolutions.