It's both 6h40m and 18h40m until 10:30. 10:30 could be 10:30 AM or 10:30 PM (22:30). Perhaps it's more of a time format problem?
I grew up with "military time", i.e. 22:30, and only recently learned AM and PM, so I'd kind of expect it to be parsed according to the user's regional settings.