I think I know what they are now, but I don't know whether they should appear in front of the channel names.
For example, for channel Phoenix, the xmltv channel ID is "I.751080.microsoft.com", and we use that to identify the channel in the xmltv file. The name of the channel should just be "Phoenix", as in the following three lines in the xmltv file:
<channel id="I.751080.microsoft.com">
<display-name>Phoenix</display-name>
</channel>
You can find the xmltv file after you run EPG setup, in folder C:\Users\<user>\AppData\Roaming\J River\Media Center 22\Temp\. You should do it without restarting MC since the Temp folder is erase upon re-starting. The file name should be something like
"<profile name> - <random number>.xml"
Open the file you should see entries like what I show above.
<channel id="I.755404.microsoft.com">
<display-name>VIVA TV</display-name>
<display-name>Viva TV</display-name>
</channel>
<channel id="I.755947.microsoft.com">
<display-name>Ciné+</display-name>
</channel>
<channel id="I.755390.microsoft.com">
<display-name>ProSieben Austria</display-name>
<display-name>ProSieben (Österreich)</display-name>
</channel>
<channel id="I.755386.microsoft.com">
<display-name>GoTV</display-name>
</channel>