The Obama number is also high because the designer combined Obama's first and second terms into one figure, unlike what he did with the other presidents who served two terms.
Stuff like this is very common. For example, at the start of Trump's second term, the whitehouse history page was changed to make democrat presidents look bad -
clinton-1 and clinton-2 are distinct. I think it's more likely collected differently. The people gathering data will change. Someone with different data standards worked there for a while.
Indeed. It took me a bit to remember why. There was a clemency program for nonviolent drug offenders with otherwise clean records who had served at least 10 years in federal prison under out of date sentencing guidelines.