Have a look on the below link for the configuring section-specific time ranges.
By default below is the data aggregation:
It is not the retention period that is causing it. I had separately created another custom report with those metrics RTT, loss rate, usage and unique users. The custom report is able to display last 7 days and even last 30 days.
I didn't touch the default storage period.
I'm afraid this is a limitation of DMI that when one metric is unavailable in given time range the whole query will not be executed. In this case it's the unique users that causes problems.
This problem is already resolved in the upcoming DC RUM 2018 release.
I will review to check what could be done to fix this issue in the 2017 version of the report.