Weddingwire Website photo formatting size

I wasn’t sure where to ask this, but what’s the correct sizing of photos for a WeddingWire webpage? I’m using the Starry Night design. It says the top photo is 1440x820 and the bottom banner photo is 1440x400. What are the units of measurement though? I tried reformatting my photos in Canva and tried doing it by pixels and by millimeters, but the photos still aren’t sized correctly when I test them out. And it looks even worse on mobile.