Tell me about it. My wife and I cannot agree on the meaning of "next" for almost anything, and we are Spanish speakers.

For example, when driving, to her "turn at the next corner" means "the corner after the next", while to me it means "the corner the car is about to cross". What I call "the next corner" to her is "this corner".

Same with days, of course.

It drives me crazy!

I don’t know if it would translate, but I’ve had good outcomes navigating with my brother by saying “following” instead of “next”. As in “okay we’re coming to Delaware street and we’ll take a left at the following intersection”. It’s not even language my brother uses but he immediately understood “next next not this next” and so I stuck with it.

Oh wow. The only context in which I (and people around me) use "next" like that is with days, which is confusing in its own right, but at least it's contained.

“Next Thursday” vs “next week Thursday”. The former, for me, means +3 and the latter +10. I don’t think there’s ever been a time when someone I know has said the former but implied +10.

Interesting to see so many people here who do interpret it that way.

In my area it's fairly common to say, for example, "X happens every Thursday. Do you want to go this Thursday or next Thursday?" which is equivalent to +3 versus +10.

Same with my wife; she tells apart "this Thursday" and "next Thursday" in exactly the way you describe. I don't. Predictably, all sorts of confusions ensue.