If you are not registered for summer course credits and you still wish to have the student health insurance this summer, then you will need to sign up for the Summer Health Insurance Extension at https://app.grad.illinois.edu/healthins/. Keep in mind that you need to have been covered by the student health insurance throughout the spring semester of 2022 to get this extension.
Furthermore, if you have a waiver-generating assistantship this summer (and appointment of at least 25% FTE but no more than 67% FTE for at least 41 days), then you will receive the 87% discount. You will pay full price without such an appointment.