When a sampling interval is configured, the station or logger will take multiple measurements within a given logging interval and then average them together to create a single logged data point.

Problem: My Smart Sensor data shows a -888.888 for a good portion of the data file.

When you relaunch a HOBO data logger, the device reverts to the beginning of its memory and starts writing new data over the old.

See attached photos for clarification.

This is also covered in each product's respective manual, which can be found on the following product web pages under the Documentation tab: