ASTNode column data

It would be great to have documentation for org.codehaus.groovy.ast.ASTNode:

getLineNumber()
getColumnNumber()
getLastLineNumber()
getLastColumnNumber()

In certain cases there seems to be a deviation from the right value (+1). However it is hard to say whether it is correct without doc. I guess it is not.
Small sample:

   ["one","two"].listIter

For "two" it gives: columnNumber=11, lastColumnNumber=16 (should it be 15?)
For the list expression: columnNumber=4,lastColumnNumber=17(should it be 16?)

Initial column numbers seem to be ok.