This is neat. It takes me back to all the triad positions on the GBE strings that my instructor always said I need to practice more than I did. I’m having trou

This is neat. It takes me back to all the triad positions on the GBE strings that my instructor always said I need to practice more than I did. I’m having trouble understanding what’s going on with the middle finger in the C dominant 9th chord in the second position.