What's guest mode?
Guest mode can let you use the Grid Diary 2 without no creating an account.
That means all of your data will only store locally on your singe device. You can sync you data with other devices.
How to do with data in the guest mode?
Once you create an account after guest mode, it will pop up a window to ask you if you would like to import you guest mode data, or discard it. So, don't worried about your data, you can decide by yourself.
Click here to learn more about sync.