section 17.2: faulty double zero

[jgmbenoit]

In section 17.2, a double zero (00) is used instead of a single zero (0) to initiate start.second to zero.

[wenbindu]

I am sure, the single zero(0) is used in the chapter.

[AllenDowney]

Will fix.
It actually works, since it is an octal zero, but it creates unnecessary confusion.