Value of FME_SERVER_WEB_URL deviant?

Hi, I am trying to generate a simple HTML page on FME Server 2017 to start an FME Server Jobsubmitter Job. I use an HTML template where I replace the server part of the URL by $(FME_SERVER_WEB_URL). We are on a secure environment and the FME Server is on URL https://myfmeserver.mycomp.nl:443/fmeserver. But when I use the FME_SERVER_WEB_URL parameter, it returns the insecure version of it: http://myfmeserver.mycomp.nl:80/fmeserver. The service URLs are configured for SSL, i.e., starting with https://. How does FME Engine "know" about its URL? What is the source of the $(FME_SERVER_WEB_URL) parameter? Thanks in advance.