Most likely just awkward rounding when the screenshot was taken. A lot of the time those post age indicator tags just count the number of hours between it and you then each multiple of 24 is a day without caring about when the actual date changes. So the first could easily have been at like 7pm one day and the second like 11am the next day and they'd both get abbreviated at 6 days ago if you were looking at it at like 4pm when you haven't quite hit the next multiple of 24 hours.