Once exported, it only fills half the screen

Hey all,

Quick question. I'm doing a project for school and have been using premiere for a while but in exporting the video, I am encountering the following issue.

It is only outputting to half the screen and I need it to be fullscreen. I have made sure all the files are the correct frame size and gone through all the normal procedures I do every time I produce a video on premiere, but this keeps happening, not matter what I try.

Does anybody know why this is the case and how to resolve it?

Thanks in advance!