Board Thread:Questions & Answers + Troubleshooting/@comment-33679346-20171117172821/@comment-33605746-20171117193110

I believe it is the order in which you bred / received them. In other words, the order in which the egg was created (for frogs you bred) or when you placed the frog in a habitat from your mailbox (for those you found in the pond or were gifted). Hope that helps.