This chart shows how many emails had their first response sent within a number of different times:
Within less than 15 minutes.
Within 1 hour.
Within 4 hours.
Within 12 hours.
Within 1 day.
Within 2 days.
Longer than 2 days.
You can highlight each bar to see the exact number for each.
Please note that this chart is subject to change due to it looking outside the range of the current report.
For example, if you send in July the first response to an email you received in May, this time taken before the first response will be reflected in that metric in the May report. If you were to look back to it, the figure will have changed.