Router won't let me Port-Forward for my Xbox One

[#1]

Having spoken to Microsoft I found out that I needed to open some ports in order to improve my horrible Xbox Live connection on my Xbox One. I go to do this in the advanced settings of my router entering all the necessary information (as shown below), only to be bluntly told I don't have access? Why is this, I need to do this in order for my Xbox to work properly as this has been driving me mad for about a year now. Thanks in advance.

[#2]

IIRC, if there's an existing setup for Xbox you need to use that and edit it. It will not let you assign the ports that are already assigned.