How to translate the title, axis labels and legend of a chart?
Here are the steps to create a translated version of a chart (or more general: a report) using the Forena module:


Make sure (core) module locale is enabled.
Instead of using the "edit" icon to change the specs of a report, use the "translate" button next to edit. Then select the language to which you want the report (chart) to be translated.
On the next screen, enter the translated report (chart) title.
You should get some informational message as in this example (in which I created a 'nl' version of drupaladmin/active_users, for which I changed the tite from "Active users" to "Actieve Gebruikers"):


  Translation, Actieve Gebruikers has been created. Switch languages to translate.
  
  Your report, nl/drupaladmin/active_users has been saved.

After switching your active language to the language for which you want to create a translated version, you'll be able to change anything of the report (charts) specs to the specs of your additional language.
In your case here, you can now modify those 4 strings


Bottomline: tranlating Forena reports is similar to translating nodes.