Appointo allows you to change the calendar invite. You can add any variable supported by us and also add any text you would like. This gives you complete control on what is added to Appointo.
Please go to General Settings > Calendar > Edit the calendar invite > Hit 'Save'.
Note: You will need to change the calendar invite for Group Appointments and Non Group Appointments separately. Which could be selected from the Drop-down on the calendar settings page.
Here is a video that will help you understand this better: