A Reporting Snapshot is an analytical tool that lets you report on historical data.
They capture data from a report at regular intervals. This data is stored in a custom object on which we can generate reports and perform trend analysis.
The Reporting snapshot is therefore the intermediate “camera” between the source report and the target object. It defines the source, target and frequency.
NB: Be cautious of the records limited number in the source report. It is possible to capture up to 2,000 records at a time. Beyond this number, the records will not be added to the target object.
Workaround this issue: will need to divide into multiple source reports dumping their data into the same target object via reporting snapshots.