Job offer?

I think I just received an offer by phone. I can't be sure. How could that be? Well...
 
I  received an email from the firm's HR to call them if I have time today. I did. HR said before the firm sends an offer to me, they want to know if $36k was acceptable to me, plus benefits, and H1B sponsorship. I was stunned, because: 1) I made more in my last job; 2) When they asked for my salary requirement, I didn't say $36k. My head was saying, ask if there is wiggle room on the "non-existent but anticipated offer" but I was too shocked to speak. Then the HR probably sensing my surprise, added that's the highest they can offer. At which point, I regained my speaking abilities, and said, I am grateful for the offer, but I would need time to think about it. I added that I just had a second interview yesterday so I would appreciate some time to process. The HR said to email or call her, when I am ready to accept. LOL. Accept what?! There isn't any offer yet. How weird is that?!

Did I just receive an offer? I suppose it was an invitation to an offer? It's not even an invitation to negotiate, seeing it was non-negotiable. Per my understanding, I was asked, if the firm were to make that kind of offer, would that be acceptable to me. I told HR, I'll call them on Monday.

I think that I didn't even have the moment to feel joy with receiving an offer. I didn't know that was possible, but I suppose it is. Now, do I email HR? This "non-offer" is now an abstract thought in my head. I am only very slightly considering it because of the H1B sponsorship. I would be accepting with the thought of leaving in two years? I am regressing! What I am looking for is a long-term position of growth, not a semi-insulting offer. (I am not a snob. I understand it is hard times. I am thankful for the offer. But I did put a reasonable salary expectation, which was not in the area of $36k. I believe I just got a low ball offer.)

I guess I will just write-off this "non-offer" in my head and move on. If I don't get any other offers, I should not really regret anything. What the "non-offer" would do for me is to buy time in the U.S., nothing more.

Stunned. But grateful.