Inbound into customs simply means that the shipment has arrived in it’s destination country, and is now being processed through the country’s customs.
Customs may hold a package for half day, 5 days, 20 days, etc. before releasing it or seizing it. Generally we tend to assume the longer the hold in customs, the more likely it has been seized. That’s not always the case, we’ve had packages held 30 days before release (unopened), so there just really isn’t a clear timeline ever. We’ve heard numerous times that Chicago customs is very slow, and very disorganized. San Francisco customs has the highest seizure rate (hence most businesses/vendors and ourselves route to JFK/New York.