In the Analytics screen, the bar chart height is correctly scaled, though the hover tooltip shows the 71.0 formatted total hours. If I switch formatting to 10:33:55 format, the total appears as 7:59:55. If I go back to decimal format (10.55) and choose Round up to next minute, it shows 8:03. If I format in minutes, it shows 479 min (but if I Round up to next minute, it shows 482 min).
Export to Excel (and grouping by day), I don't see this problem (it shows 8.0):
I'm reluctant to share database backup without some approval from my employers, since they're fussy about leaking information, but if you can't figure it out from what I can give you, I can talk to them about whether it is okay.