Keeper.sh now writes your busy time into a Google calendar you connect. You choose which of your connected calendars feed it, and events from a calendar you have not mapped to that destination are never written.
Each mapping runs one way. A work calendar can feed your personal one without the reverse, and a shared calendar you only read can stay out of both. Set up the reverse connection as well when you want events to travel in both directions.
Keeper.sh tracks every event it creates in the destination. When the original changes or is deleted, the copy is updated or removed to match, so the destination does not fill up with stale blocks.
Sending events to another calendar explains connections, direction and how quickly a change lands.