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