on the twentyfifteen theme. When I click on the customizer to set my header, There is some text there that says. "While you can crop images to your liking after clicking Add new image, your theme recommends a header size of 954 × 1300 pixels." I need to change the 954 x 1300 but I can't find where it is being generated from. I have tried various filters but nothing has worked.
How can I change those dimensions in the text?