Xpath in Email Template in Workbench ES

Hello,

Can any one please show me how to put xpath in the email template of the "Assign Task" in workbench ES so when it generate email, it will pull the user name(e.g.John Smit) from whoever submit the form in the subject email. I try different things but I can not get the right one instead get only creator_id. I know I miss something but I could not tell what is it. Can any one please help.

Thanks,

Han Dao