There is a curious problem on the Baseball Reference site with the total earned runs for the Minnesota Twins. While the total earned runs of the team is 724, the sum of the individual earned runs for the individual pitchers is 726.
While the team totals at the bottom of columns on Baseball Reference appear as if they are based on the data in the table, it looks like at least some of them are sourced differently. The major league baseball site agrees with Baseball Reference on the team total of 724, so apparently the Baseball Reference individual pitcher stats are off. But its also apparent that their team summaries are not necessarily based on the individual player data.
If you use this data regularly, as I do, you might want to be careful.
Update: As the posts below note, baseball rules allow assignment of an earned run to a reliever while making it unearned for the team. So the "team totals" are accurate, they just aren't totals of the numbers in the columns above them.