Meeting at subway station

This may be a stupid question especially because I speak Japanese and have been to Japan many times, but a friend wants to meet at exit 5 of a large subway station. I usually meet friends at a shop or the subway gate, but this is just an exit. Does it mean street level, downstairs in the station, or is there no convention for this? I am staying near the station so will be coming at ground level.

Ask your friend. But shouldn�ft be too difficult to find her/him.

Actually, I would say it is indeed difficult. An exit number can mean above the stairs, below the stairs, more than one staircase or even a ticket gate. People nowadays seem to rely on their mobile phones to meet each other, but I know people who couldn't meet even with their phones.

There is an official map for every station building. Study it well to make sure you're both looking at the same thing. (If you could name the station, perhaps someone could find the map for you.)

But usually, large stations have a "meeting spot" (like Hachiko for Shibuya Station or Gin-no-suzu for Tokyo Station). It's best to meet there.

Of course, you can suggest to meet at a shop, but sometimes there are no shops near your destination, and maybe your friend doesn't want to spend for the shop.

There's no hard and fast grammatical rule for it. In practice, it doesn't make too big of a difference, since if you and a friend decide to meet at, for example. "Exit 5" of a subway station, there are really only three possibilities:
1. Exit 5 is a stairway, and you'll meet at the bottom
2. Exit 5 is a stairway, and you'll meet at the top
3. Exit 5 connects directly from the station to some other underground building entrance or passageway (so you'll meet where the connection is)

If it's a stairway, oftentimes you can see the top from the bottom, and vice-versa. Since that's not always the case, though, my friends and I tend to specify "Let's meet at the top of the Exit 5 stairway" or "Let's meet at the bottom of the Exit 5 stairway," to save whoever gets there first the hassle of maybe walking up and down to check the two possible spots. If you want to save yourself those extra steps, then double-checking with your friend about whether they want to meet at the top or the bottom is the best bet.

Personally for me whenever I've arranged to meet someone at a particular station exit I've always taken it to mean outside the station at the exit. But I can see how some people might interpret it differently.

Honestly just ask your friend. I don't think they will think badly of you for wanting clarification (and if they do then do you really want them as a friend?)

I'd suggest outside the gates.

But ask you friend.

Be pedantic and ask them to specify. Normally I would expect it to mean at street level of the particular exit, and with numbered exits that makes things a bit easier.
As a counter example, I had someone wanting to meet me at the east exit of Shinjuku and I immediately replied "which one?" as I could think of at least three different "east" exits as well as all the other possibilities within the building or street level.

And similarly to the "East Exit" example, there are often subway stations in Japan with exists like "5a" and "5b".

I've also had someone say to me decades ago, "Could you translate for me and tell her that I want to meet her at Exit A of the station?" and I said, "Okay, but are you sure she knows where Exit A is? Because I can't recall an Exit A at that station." The foreign speaker had assumed that all train stations in the world would at least have an "Exit A". Of course, I suggested meeting at the "Moyai".

Typo. I knew something was wrong.

Incorrect: exists
Correct: exits