Changing screen resolution changes canvas size

Not sure if this is a bug, a limitation or a compatibility issue, but here goes;
I normally do my development on an iMac with a screen resolution of 2304 x 1296. While taking a trip (and hoping to get in a little coding time on the train), I’m using a MacBook Pro using a resolution of 1650 x 1050 (because old eyes can’t handle small fonts). The canvas size is 1024 x 1024, so there shouldn’t be an issue of scaling. The game has borders around the main play area to prevent the pieces from being dragged off the canvas, so I know where the 1024 x 1024 box should be. While testing using Preview Mode on the 1650 x 1050 resolution, I noticed that there was additional space to the left of the right border, so I added a quick “display mouse coordinates” to the screen and discovered that the size of the X axis (and only the X axis) was now 1082 instead of 1024. Experimenting around, I decreased the resolution to 1440 x 900 and found that the X axis was now 1458. If I increase the resolution to 2048 x 1280 or higher, the extra “canvas” no longer displays and the coordinates do not exceed 1024 in either direction.
Example at 1650 x 1050 resolution:

Thanks for looking into this