My crontab file has lines similiar to :
# DO NOT EDIT THIS FILE – edit the master and reinstall.
# (/tmp/crontab.31994 installed on Fri Apr 16 09:43:07 2004)
# (Cron version — $Id: crontab.c,v 2.13 1994/01/17 03:20:37 vixie Exp $)
at the top. I did not add these. How did they get there?
Those lines are added automatically by the crontab system when you update your crontab. You can ignore them. They are comment lines and do not affect the running of your crontab.