This may just be the wrong behavior from what people expect. The center percent is just the percent that are not convinced of the selected filters. So depending on what you select, that will change.
We, in fact, do have a presumption of innocence in the US. So yes, other than those convicted of crimes, others are non-convicted detainees. These people may be detained for quite a long time, too. That is the point this dashboard is making
Could you specifically explain what that 71.2% figure is?
Edit: Ah, if you hold your phone rotated the label “Not Convicted” appears. That is… a very odd way of spinning this data.