possible typo in variable description

In the Chapter 2 exercises, `parity` is described as "the number of people in the respondent's household". Based on the [codebook description](http://www.icpsr.umich.edu/nsfg6/Controller?displayPage=labelDetails&fileCode=PREG&section=A&subSec=8018&srtLabel=611964), I believe it should be "the total number of live births".

Apologies if I'm overlooking something, and thanks for the exercises!