This dialog has useful instructions on the dialog itself.
Go To What:
This list determines what sort of thing you will go to, the target. ‘Page’ moves you to the top of a page, while ‘Line’ moves you to the beginning of a line. [Note: this is broken. Go To absolute behaves like this. Go To relative behaves like pressing the up and down arrows. I can’t reach bugzilla at the moment to report this.]
Number
This editable box determines which target you move to. If you simply type a number, the insertion point is moved to that target, counting from the beginning of the document. If you type + or - a number, the insertion point is moved forward (for +) or back (for -) that number of targets.
Prev
This button moves the insertion point to the previous target.
Next
This button moves the insertion point to the next target.
Go To
This button moves the insertion point to the target specified in the ‘Number’ box.
Close
This button closes the dialog.