journal entries

please explain the calculations with finding the numbers for the months. i dont understand how to work it.

Edmiston Company owns bonds of another corporation that pay annual interest of $800. These bonds were purchased on April 1, 2020, and the next interest payment will be received on April 1, 2021. A two-year insurance policy was purchased on June 1, 2020. The $1,200 insurance premium was paid on that date and was debited to Prepaid Insurance. Service Revenue was credited for $900 on June 1, 2020. The amount represents a one-year advance payment for services to be performed by Edminston Company through May 31, 2021