When a USPS package is in Transit it means that the package is on a truck or plane being transferred to a different sorting facility.
That new sorting facility could be 20 miles away or it could be 100 miles to 1,000 miles away so it can vary as to the time it takes for the package to be in transit.
Some packages may stay in transit for one day and then some packages that are traveling farther may stay in transit for a few more days.
When the package is in transit the tracking will not update until the package reaches the sorting facility and then gets off the truck or plane to be handled and then scanned.
When it gets to your location then the tracking info for USPS should update to say it's arrived at your local post office.