When I open a photo for which I'd like to resize the dpi in Affinity Photo, I go to Resize Document and I see the default dpi is 72. When I change the dpi to 150, the pixels adjust accordingly. However, when I export that photo, reimport to Affinity Photo, and go back to Resize Document, it shows dpi as 72 again. Why does it not show 150? Any insight would be greatly appreciated as I want to ensure these are best quality for printing. Thanks!