I have compacted my pst file several times, but the file is still 6x larger than the total size of the folders (when I right click on "personal folder" in outlook). Why is the actual file so big? Is there something hidden inside that I don't know about?

main pst file size is 2.7gb, but the "Total size" of the personal folder is only 292mb. Any thoughts? Thanks.

details...
My outlook pst file was about 5gb. I turned on autoarchive and ran it, sending older "deleted" and "sent" items into a new archive.pst that was created. I did not archive any other folders, calendar, tasks, etc.

main pst file is 2.7gb
main personal folder "total size" is 292mb

archive pst file is 1.9gb
archive folder is 1.7gb

1.9 + 1.7 = 4.6gb, which is close to the original 5gb file, no worries. The archive folder and file are pretty close, but the main pst is way off.