how to proceed wrong item given after win?

you could ask support to change the giveaway game assuming it isn't a free one.

If you mark it as not received, it automatically doesn't show up as unredeemed win, so you're all done, not much more you can do if the creator doesn't reply.

leave a comment at the giveaway stating what happened or add them on steam to inform them. If he doesn't respond there's nothing you can do.
And marking as not received doesn't count as a non activated win.

Edit: Checked the giveaway and I hiiiiiiiiiighly doubt you'll hear back from him

You're fine as it is, it would be the giveaway creator to be known as someone who didn't give the item he promised.
In cases like this, you would ask him to send a ticket to change the giveaway to the correct item, but that DLC can't be given away, as it's not directly available on Steam.
Perhaps he tried to exploit the system by giving away a free item under the guise of something with a similar name...
Or maybe it was just an accident, but until he answers we can't know for sure...

You're doing everything right so far. The important thing is, no matter what happens, do not mark it as received if you don't have it on your account. The ball's in the giver's court now. Ideally he'll get in touch with you and figure out what went wrong. Then maybe he'll provide you with a working gift for the game, or decide to eat a "not received", or even ask support to delete or retroactively change the giveaway (which they usually do only if the winner agrees).