Frame size 9:16 appears as 8:13

When I change the frame size in a sequence to 900x1600 or 1080x1920 it does not appear as 9:16 but 8:13. When exported to pc, the dimensions in "get info" are 984x1600. I'm trying to export a vertical video to share on social media, I'm using Airdrop to share the file with my iPhone. The frame size is odd, so my iPhone won't detect it as a video and says that it "failed to save item." Some screenshots:

I've searched everywhere for an answer, but vertical videos seem to be quite an undiscussed topic.