What this measures
Work that leaves no trace in git.
Someone who spends a week keeping servers alive produces no commits and reads as idle everywhere else in this platform. CloudTrail is the only record that the work happened and who did it.
A CloudTrail write is not a unit of work, so events are weighted rather than counted. Signing in, changing your own password and opening a CloudShell terminal are all writes, and all score zero — presence is not delivery. Creating a load balancer and toggling a notification setting are both one row, and are not worth the same.
Only 90 days exist. No CloudTrail trail is configured on this account, so nothing before the retention edge can ever be recovered. An empty period means “not retained”, never “nothing happened”.
No infrastructure changes recorded in this period. Either none happened, the window predates CloudTrail’s 90-day retention, or the ingest has not run — check Sources.