SetRangerUser didn't work

Hi everyone,
After running my codes, I can get some results as follow.



I used the SetRangeUser command and want to change the x axis range from 20 to 30, as what I did in the attachment. But the figure didn’t change after I used this command.
How can I fix this problem?
Best reagrds
Peng

May be this can help you:

root.cern.ch/drupal/content/how-set-ranges-axis