I will give up... wanting more comparable data doesn't change any of these guesses... I'm not sure what you are fighting for.They chose one day sales because it sold more than all of their previous games. What’s so hard to understand? Announcing 2.5M in 24 hours is better than any other number after 3 days. They didn’t do that before because sales numbers were not that high.
They will be doing more sales milestones of course. This won’t be the only one.
Cheers.
Edit - I changed a bit the text because there is really not need for it.