No, the point of the joke is that the mathematician uses natural numbers (0,..) and everyone else uses ordinal numbers (1rst, 2nd, ...) so when his wife asked for 12 he thought she meant 0-12. What she actually meant was 1-12. So it was a miscommunication caused both by his habit of using natural numbers for everything and being very isolated from the outside world.

I'm reluctant to continue dissecting what after all is only a joke, but:

1. The mathematician's wife was not using ordinal numbers; nor was he. They were both asking "how many of these things are there?". Cardinals, not ordinals.

2. A mathematician who's so used to 0-based working that he always counts from 0 simply will not interpret "0,1,...,11" as meaning that there are 11 things. The same unusual way of looking at things that makes him start from 0 will also make him proceed from "...,10,11" to "there are 12 things".

3. The mathematician's wife didn't "ask for 12". She left him with 12 packages. What happens in the joke is not a miscommunication, it's s slip-up by the mathematician in going from "...,10,11" to "12 things". Which I suggest is highly implausible for a mathematician in whom 0-based counting is deeply ingrained.

And now I've had enough of overanalysing this joke and shall leave it alone. Feel free to have the last word if you wish.

Incidentally, (some) mathematicians prefer their ordinals to start from 0 as well. The trouble is that "first" (derived from "foremost") really ought to mean the one you start with rather than the one numbered 1, and "second" (from the Latin "secundus" meaning "following") really ought to mean the one after that, and "third" etc. are derived from the number names and therefore have to correspond to 3,4,... -- so there's a gap at 2. One of my acquaintances therefore likes to use a sequence of ordinals that goes: first (0th), second (1nd), twifth (2th), third (3rd), fourth (4th), fifth (5th), etc. I don't think it'll catch on.