Anyone can explain "Document #" to me?

[bluescharp]

I don't know how to set "Document #". "0","0;_0","0;_0;0"...what does it mean?

 

[rostonix]

That means that page has several documents in it which are loaded separately.
If you use action designer (right click on element on recording tab) then ZennoPoster will choose correct document # of chosen element automatically.