Control group numbers in the CD version go from 1-9. The appearance of those numbers next to the unit depends on a graphics SLP. In the HD edition (and therefore in the compatibility patch, which uses HD edition files instead of CD ones), an extra 0 was added to this SLP. This leads to the effect that when used offline, Control Group 1 shows as 0, Control Group 2 as 1, etc.

To fix this, you can replace the Age2HD/data/interface.drs file with this one: [You must login to view link]

However, Voobly itself uses a seperate fix for this which shifts numbers by one, which means if the file is replaced as above, this leads to Control Group 1 showing as 2, etc. when playing on Voobly with the comp patch and the modified interface drs.

To fix this sideeffect from the previous fix, you can use this mod. Hopefully this will just be a temporary workaround and the issue can be fixed directly in the compatibility patch eventually.