You're absolutely correct. We're up to president 45 and 8 have died in office (4 of natural causes, 4 assassinations).
If you take those 8 and put it on the chart above (it looks like per 100,000 workers, correct?) then it would be 17, 778.
Of course, if you just use the 4 assassinations (fatal injuries) then it comes out to 8889.
Really makes you think.