I have started using logwatch to check everything is ok on my servers but under pam_unix I am getting:-

cron:
Sessions Opened:
root: 78 Time(s)

and my other server

cron:
Sessions Opened:
root: 30 Time(s)

What does this actually mean and is it something to be worried about?

These are cron jobs. Look at the ones you have with "crontab -u root -l" and in the /etc/cron* directories.

Ah ok that is what I thought, just wanted to check it was not a security breach.