Collections are 0-based; the 1st item is index 0, the 2nd item is index 1, etc. DayOfWeek, on the other hands, returns values from 1 to 7. So you need to subtract 1 from the day of week value.
GetAt(Task.Coll1, DayOfWeek(AddHours(Flow.StartDateTimeUtc, -7))-1)
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Melissa Bailey
Genesys - Employees
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