How Long should it be after USPS "in Transit" mean?

If you paid for 2-day priority, chances are you'll get it 2 days after it's shipped to you. My hunch is that will be Thursday, which is the expected delivery date.

Nothing is scanned (and therefore nothing can be tracked) while it is in transit It will be scanned when it reaches the next sorting center, which will probably be the center nearest you.

Don't check for new tracking every 20 minutes. Nothing will change in 20 minutes -- or even in an hour. Tracking isn't automatic. Parcels don't have tracking chips in them. They have to be scanned individually by man or machine in order to be tracked. When was the last time you checked for new tracking? Don't do it again for at least 15 hours or so. (And I said "15 hours" because you paid for 2-day priority. If it was coming by regular 1st class mail, you shouldn't check more than once a day.)

"shipment accepted".

at 6:10 pm on July 25

How long will will it say this before it actually ships out to me?

It will say that until it says something else.

It is being shipped priority 2 day mail so I am wondering why the estimated delivery time is Thursday if it was accepted on monday.

Maybe use common sense. Do you think mail that is received at 8:00AM or 11 PM gets delivered exactly 48 hours later?

Day one ends Tuesday night. Day Two ends Wednesday night. Delivery is normal the next day in your case Thursday. Most mail gets delivered ONCE A DAY.

It may or may not be there. ESTIMATED means Estimated. Not carved in stone. It could be earlier it could be later.

Checking every five minutes will not get it to you any faster. Mail moves from one sorting place to the next usually Once a day. Sometimes more for some stations .

Parcels DO NOT move one at a time from Postal Plant to Postal Plant to you.

Gathered sorted moved to a place closer to you . Sorted again could be many times before it gets to the Post Office that YOUR Mailman gets the mail for his route.

ESTIMATED is just that a Very good GUESS.

If the time that it was accepted, the truck had not yet left, then your package would have been sent to the Distribution Center that same day, where it was sorted and put on a truck early Tuesday. It should arrive on Wednesday. If at 6:10 Monday there was no transport that evening, it should arrive on Thursday. All mail gets processed as soon as possible.