Configure the pixel adjustment between window.open widths sourced from IE mode pages vs. Edge mode pages

This setting lets you specify a custom adjustment to the width of popup windows generated via window.open from the Internet Explorer mode site. If you configure this policy, Microsoft Edge will add the adjustment value to the width, in pixels. The exact difference depends on the UI configuration of both IE and Edge, but a typical difference is 4. If you disable or don't configure this policy, Microsoft Edge will treat IE mode window.open the same as Edge mode window.open in window width calculations.