If you have a row set to layout: box, the max width of the row is 1170px with 15px of padding on either side. If you are using layout: wide, then the max width of the row will be the width of the viewport (browser) minus 15px of padding on either side.
But the grid is responsive, so if you adjust your viewport, then the grid will resize, which will shrink the row width and possibly the application width depending on how you have your application configured. If you have used HTML to force a 400px width on the application card, then you may see no changes. If you are using an application card with a spacer card, then the application card may grow smaller to maintain an ~50% layout. If you are using an application card and the spacer card is hidden on mobile, then the application card will expand to fill the full-width of the row and will be the size of the viewport.
