Discovered unix system accounting tools

So I was browsing around my laptop, which by incident found, acct. Which is a set of unix system accounting tools. Which from documents stored on my laptop, have:
- accton: which use to turn on/off system accounting
- ac: to show user connect time
- sa: summarize system accounting info.
- lastcomm: which printout previously executed command.
:
ac, is to print out user connect info. Which if executed directly just print out:

sweemeng@sweemeng-laptop:~$ ac
total 82.92

which really nothing, but it have a few parameter