The time period to display statistics for DSpace objects in the UI is currently not configurable. Only the previous six months plus the current month of statistics are displayed. There is a pull request open to add the option to include additional months of statistics (
https://github.com/DSpace/DSpace/pull/10142), but it has not been included in the DSpace codebase yet. So far, there hasn't been any interest in this work, but it's possible that could change. If you or someone at your institution could test the pull request that would help to make it available in a future version of DSpace.