Tax withholding on multiple jobs?

How will my taxes be affected if I have two jobs? My main job is about $60K/yr and the other is just a part-time thing I did when I was a student and I'll continue to do (less than $1K/yr). When I fill out the W-4 form for my main job, I get an additional *negative* $70 withheld from each paycheck. Does this sound right?