Short answer
HubSpot's KB: a restorable delete keeps the contact in the recycle bin for 90 days; restoring brings back activities and analytics. Engagement reports like Productivity still count calls, meetings and tasks of deleted contacts. A permanent delete can't be undone.
1. In HubSpot
The relevant screen in my demo portal.
2. Worth knowing
Use permanent deletion only when a privacy request requires it.
3. Related
Bulk deleting contacts and the audit log.