
Hint: 8x 4x 2x breeding
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Edit: oops, sorry, I didn't knew, it's VIP only
Because people are still asking:
Since one of the latest updates there are more breeding options available, depending on how much space you have left for eggs.
It's on the left of the usual [breed] button.
[8x] [4×] [2×] [breed]
If I have only Space for 2 more eggs, only 2× can be used.
The less frogs you already have (the newer the frog species is for you) in your froggydex, the more frogs in the breeding screen are still sleeping and the higher button makes more sense in an economic view.