What to put for base plan ID? (New Google Play Console Update)

I am trying to create some new subscriptions on Google Play console and have created a new product with a matching product ID on RevenueCat and in the Google Play console. After creating the new product on the Play Console, I have to add a “Base Plan” and give it a unique “Base Plan ID”. What should I put for the “Base Plan ID”? Should I put the product ID as the base plan ID as well? I know these are new changes to the Play Console, so appreciate any guidance I can get on this.