Is a sadistic host inviting you to nibble on peanuts at a time when any red-blooded American has already eaten dinner?
Is a disorganised hostess confused about guest's intestinal needs at such an hour?
Is this party going to last 25 minutes, so that you can all still get dinner at a reasonable time afterward?
Nothing of the sort.
This is an apologetic Italian dinner invitation. It is apologetic because when an Italian hears "dinner," this calls to mind certain expectations about antipasto, primo, secondo, contorni, formaggi, frutta, e dolce. Because of this, your host does not dare to say "dinner," but must instead humbly refer to their spread as an "appetiser."
Since an American has almost none of these things in mind when it comes to dinner, here it the invitation in translation:
"Dear guest, please come to my house for tons and tons of food at the dinner hour. I'm terribly sorry, but I'm not going to bust my ass to iron my table linens, get all the right glasses out, and bring out the right courses in the right order. We might not even sit down all at the same time. But you will eat. And it will be dinner. I'm sorry I'm not sorry."