"month" shows the number of votes since January 1, "week" the number of votes since January 6, and "day" shows today's votes. All the dates are UTC based, which means the day starts differently from what you consider your day; even in UK, the day coincide just in a specific period of time (not when UK uses UTC+1 as timezone).
For the days between January 1, and January 5, the votes were:
- month: the votes since January 1
- week: the votes since December 30, 2012
This is because the week on Stack Exchange always starts on Sunday, midnight UTC.