You have to edit keypad Macro keys.
I'm going straight into the settings:In the Menu Bar 'View|Macro keys...',
When you open the 'System->Keypad folder' you should be able to see the inherited (or default) settings for your keypad. Change the value for KEY6 from 'e' to 'o' and save it.
This will create a new (duplicate) setting for your KEY6 Macro key which will supersede the existing inherited or default settings (which are always loaded). Save it into your primary settings file to continue to use it.