IText issue

[Raj kalaria]

I am completely new in IText and am totally confused as where to start from.

I have one issue. The Code is written by some one else and I am trying to understand the code.
Here is the snippet of the code
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textLeft = pdfStamper.getOverContent(currentPage);
        textLeft.beginText();
        textLeft.setFontAndSize(font, 12);
      [b]  textLeft.setTextMatrix(160, 694);[/b]
       // textLeft.setTextMatrix(160, 700);
        textLeft.showText(versionNumber);        
        textLeft.endText();

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How does the measuring of the co-ordinates takes place in Itext. For Instance, if i need to modify the co-ordinates to new position, how can i get the correct off set value?
textLeft.setTextMatrix(160, 694)