The point-to-point distance was only 26.8 meters (88 ft), but the path covered 127.4 meters (418 ft). I'm assuming they were gathering data with the RIMFAX instrument.
RIMFAX is a ground-penetrating radar on the rover, it uses radar waves to see geologic features under the surface. The device can make detections perhaps dozens of meters/yards underneath ground, such as for buried sand dunes or lava feature, or in this case maybe they were identifying the underlying strata that formed these delta deposits.
