I edited the name of the two milestone (1.0, 2.0) I found in the build-in ticket-system. I changed the name of the second to 1.0 that was equal to the name of the first at that time. Then changing the name of the first always change the name of the second to the same name as well.
I've confirmed what the user is seeing on the "Edit Milestones" page.
I was able to find that going to Admin -> Tools, Field Management allowed me to change the name of one of the milestones without affecting the other as a workaround though.