This week, next week

I was sitting in the waiting room - waiting. That's why they call it a waiting room. An elderly man (that means more elderly than me) came in and asked if he could make an appointment for next Thursday. I listened as the receptionist said that was easy and named a time for Thursday 23rd. He nodded happily and went on to say how he'd been there ages before and had been helped and he had the same problem and was expecting the similar fix.So I figured he didn't want to wait too long for his appointment. I wondered if he had heard the date because that day was Tuesday 14th.
The receptionist went on to suggest that they would ring and remind him and that he must let them know if he wanted to cancel. I watched and saw the look of surprise about this. I could contain myself no longer. I popped up to clarify. Did he mean the Thursday in two days time or the one in the following week which as the date quoted? And so it got sorted out.
I have seen others and particularly American friends completely bamboozled by such Aussie usage. If it's Tuesday then the day in two days' time is THIS Thursday and NEXT Thursday is the one in next week. Inst' it? I've pondered whether it makes a difference where you are in the week. If he had come in on Friday and asked for an appointment next Thursday would it have been clear? Does it only become this Thursday when it is close?
Ah, the subtlety of language. I will have to think some more about this. Perhaps next Friday...

PS My sister wants to know the derivation of 'to spit chips'. Can any of you language types help? Google has some idea which sounds spurious.