Paketanweisung

05:51 Jul 3, 2023 

I believe the writer informed the recipient in a letter that they were going to receive a package. The sender included a part of the postal receipt (which they got at the post office as proof of paying the postage) with the letter so the recipient can pick up that package from their local post office.
It may be similar to a Postanweisung, where someone pays in cash at a post office and sends the receipt to another person who can then go to their post office and withdraw the same sum. https://de.wikipedia.org/wiki/Postanweisung

05:40 Jul 2, 2023 

Thanks for the quick reply! I had to change the last part of my post a bit, regarding my alternate interpretation, since I first assumed we're talking about a male recipient, but--of course--I can't know that. Though whatever interpretation is more likely, the result is essentially the same.

Best of luck

05:27 Jul 2, 2023 

Yes, that does make sense in this context! Thank you.

05:22 Jul 2, 2023 

In this context, "Paketanweisung" could mean "Paketsendung"; basically, the friend is thanking them for "instructing" someone to deliver a package (=the gift).

Does this make sense to you?

Best wishes

PS
Alternatively, the intended recipient of the package may have written this thank-you message after they were informed that, e.g., the post office had a package for them.