I have a feature class in a (10.5.1) MXD. I go into Properties --> Display and customize the display expression so that it shows up with some verbiage and the value in the field rather than just the value (which in this case would be a 3):
And then export it as a service (on our in-house install of ArcGIS Enterprise). When I pull the service back into a another MXD it is showing only the field value again:
What tweak do I need to do to have it show up with the customized display?