If the highest you've got on 'Become Legend' is 4/5, that means the highest Glory rank you've ever achieved is Mythic. 1/5 - Brave, 2/5 - Heroic, 3/5 - Fabled, 4/5 - Mythic, 5/5 - Legend. So that all checks out. You've never hit Legend so A Glorious Legend should be 0/3. Do you believe you've hit Legend rank in Glory at one time? Or at different times in multiple seasons?