PokerTracker

I opened this table in my PT3 DB:

http://imageshack.us/photo/my-images/651/1402l.png/

Why do we consider here 4 positions where we have only two players at the beginning of hand? I thought we should have only SB and BB in this case. What exactly I do not understand?

I want to change the separation of the positions for EP MP LP. And I lack a full understanding of how the table works.
Now i think that in HU statistics are written to the CO and BU (not only to SB and BB how it should be how i think), but if not, so then we can delete button and co positions when we have 2 players only from this table.

Not exactly - you can have two players at the table without any small blind if the table was three handed and a player left - that's why we need the button. The last time we looked at these we found there was a need for CO as well in very specific cases, though I can't remember off the top of my head exactly what that was.