Why, at times, is data displayed in the Sent and Complete columns on the Surveys explorer out of date?

Environment: 

Outreach and Feedback surveys and mailings

Because the data displayed on the Surveys and Mailings explorers requires processing by back-end utilities, the report results may be temporarily out-of-date.

Resolution:

To view the most up-to-date results of your surveys and mailings, go to the Summary tab on the survey or mailing itself. The data that displays on the Summary tab is current as soon as your survey or mailing finishes sending.