How to shorten this address format for online orders?

Hi,

When I moved into my apartment a few years ago, my address was given to me in the following format (of course, it's not really my address; I've given a different street and different numbers, etc., just so you know what the address format looks like):

Monika Musterfrau

Test lane 19-20 Stage 4 Top 16

Postal Code City

country

So, 19-20 is obviously the house number of the building where my apartment is located, and Stg. is the abbreviation for the staircase where my apartment is located. I don't know what "Top 16" means. Does anyone know what it stands for? There are no numbers on the apartment doors, so I don't know if that's the number of my apartment or what else it could mean?

When I order something online, this long address format is very tedious (the actual name of the lane is also quite a bit longer than "Testgasse"). Sometimes not every line fits on the address label or whatever it's called, and then it looks really odd. I'm worried that a package might get lost because of this. It's happened once, but I have no idea if it had something to do with the long address format that might not fit on the label. I'm also worried that packages might get lost if I shorten the address incorrectly, because I don't know, for example, what the "Top" means. I've never seen that happen with an address before. Could I shorten the address for online orders like this:

Monika Musterfrau

Test lane 19-20 4/16

Postal Code City

country

Would it be correct to shorten it like that, given the address format? Would the postman know what the 4 and 16 stand for? I just don't know what the 16 stands for. P.S. There aren't that many apartments in my building—25 at most, more like 15—so it's not a huge apartment block. I don't know if that would make it easier for the postman to find the apartment, but since postmen generally don't put much effort into it, I want to shorten the address so that it's understandable, so my apartment can be found, and thus the package can be delivered.