For the Appomattox campaign, the chart shows 10,780 casualties for Grant; none for Lee. That’s obviously incorrect. Lee’s army suffered numbers of casualties from the time when the Petersburg defenses were evacuated to the surrender at Appomattox.
I copied that chart to Excel and did some calculations.
Total casualties comes to 506,359.
Comparison of Grant/Sherman (which includes Thomas but not Sheridan) to their opponents: Grant/Sherman: 88,733; Opponents: 111,458.
A curious omission. Just a couple of weeks ago I happened to be traveling near Appomattox, and had a few hours, so stopped in to visit the park there. They have all the details of the final battles, including casualty statistics. So the numbers are readily available.
They put the total war dead at (IIRC) 624,000 and since it's a national park, I'd presume that some kind of "official number."
In that final battle, near Appomattox, one civilian was killed -- a slave woman who did not evacuate with the others, was struck in her home by a stray bullet, and later died. According to the rangers, that was very typical of Civil War civilian deaths.
Finally, on the question of who had the more casualties, I think it was invariably true, that if the defenders stood their prepared ground, then the attacking army would suffer far more casualties.