In answer to your question I would use “released in”
Now having said that most of what parishiltons says is correct. It is a very lazy ATC technique although the ATCO may be trying to be helpful. The example I have seen regularly is an aircraft 10 miles from the UIR boundary requesting descent because it has reached its top of descent point for its destination in the adjacent UIR/FIR. Instead of phoning up the next UIR the ATCO will tell the aircraft to contact xxxx on yyyyyy and tell them you are released in zzzz Airspace. The ATCO would only do this if there was
no conflicting traffic to the aircraft involved.
As you you get older and wiser and it becomes a regular occurrence for this flight you can always pre empt the situation by coordinating an early descent in advance.
Rgds
AyrTC