Problem with postindex table

[vbdarwin]

Hi all

I emptied and rebuild (using canonical Vb procedure) postindex table.

Afted job completation, postindex # of records gone from ~81,500,000 to ~14,700,000.
About 66,800,000 records seems to be lost.

What can be happened?
Thank you

--------------- Added 1295948337 at 1295948337 ---------------

Addendum:

After rebuilding I also discovered that records in word table gone from ~1.384.000 to ~428.000

What happened?
How is possible?
Is this correct? No data loss?
Where can I find some documentation about relations betweeb post, postindex and word tables?

Please help!
Thank you

Thank you.