The % stats for the current day currently compares the numbers from the entirety of the previous day. So the negative stats are misleading (mostly).
It makes sense to show this only for data accumulated across the same time intervals?
Yes, you are right. We will take a better look at the current day view. We have some ideas on how to improve it. We might change it to “last 24h” instead of today. That way, you can compare it better with the previous 24 hours.