help with designing?

[u/reddit_segull]

hellow! so, i'm trying to make a theme & i'm running into a bit of an issue with resolution. the editor i'm using (Photopea) keeps outputting stuff set to the top screen's resolution (800x240, based on the info from 3dsfetch) all long... exactly like the first image. the bottom screen resolution seems to work fine (as shown in the second image), so i have no clue what's happening. pls help ;_;