How the shipping process works:

When we ship packages out, they get picked up in bulk by USPS and scanned at a Central Distribution facility. This is when the tracking number is updated. The packages then get scanned when they are in route.

The cause of the issue:

They do not scan the packages when they come in. It gets scanned after its transported to the central distribution facility. 

Sometimes, when the item is shipped out by the end of the business day, it doesn't get scanned in the Central Distribution facility until the next day. That creates a delay in updating the tracking number, leaving many customers confused.