unix top command (memory usage)

in unix when i use top
i get an output like this:

load averages: 0.64, 0.57, 0.53 14:04:42
347 processes: 1 running, 1 waiting, 169 sleeping, 172 idle, 4 stopped
CPU states: 16.4% user, 2.8% nice, 7.6% system, 73.0% idle
Memory: Real: 1532M/3964M act/tot Virtual: 7767M/45341M use/tot Free: 75M

my question is why we dont get the total memory when we add Free memory
to actual memory?

1532(act)+75(free)!=3964 (total)
and
7767(use)+75(free)!=45431(total)

and my second question is:
what kind of information we can get from the first line
(load averages: 0.64, 0.57, 0.53 )

and lastly:
i have a system>> Compaq Tru64 UNIX V5.1B

how can i get information about swap activity?

Top isn't showing you info on wired pages (pages in use that can't be used for paging).

Use "vmstat -P" to get a breakdown on memory usage.

Total memory = (Active Pages + UBC Pages + Wired Pages + Free Pages) * 8192/1048576

Top's act = (Active Pages + UBC PAges) * 8192/1048576
Top's Free = Free Pages * 8192/1048576

Use "swapon -s" for swap used/total, and "vmstat -s" for detailed info about swap activity.

In response to your second question.
The load is usually the averaged number of processes in the run queue
waiting for a context switch for the last minute, five minutes, and quater of an hour.
So the longer the queue the poorer your processing performance.
But I would say that the manpage of top or uptime should tell what is displayed.