Custom Document Size Export Issue

Hello, I’m trying to figure out what size I should be setting my document to. I was trying to create a canvas with the intended size: 8.127 x 10.253 in. When converting this to pixels at 300dpi in photoshop, I show 2438 x 3076 but when I entered this into the page designer app and exported, my document was something like 24 inches wide (3x the size). Please help!