I Asked for 21 Days of Prices and Got 147 Rows. Only 21 Were the Trip I Asked For

A one-way price calendar is a list of days. Add a return date and the same request becomes a departure × return grid — seven times the rows, trip lengths from 1 to 13 days, and a "cheapest dates" field that stops answering the question you asked. Measured on two runs of the same route today.