Create a Pathfinder Society Summoner with race half-elf.
The Favored class category says to select 2, but after selecting Summoner for the first and then selecting Bonus Eidolon Evolution, the 2nd Favored class does not allow you to select Summoner again. Clicking the Add Selected button when Summoner is selected does nothing.
This is as designed. You can't take the same class twice. IF you're multi-class it lets you choose two. If you only have one class then you have no way to select another favoured class.
Then how does one select the second Bonus Eidelon Evolution?
How many levels doe you have in Summoner?
1 level Summoner, but half-elves get Multitalented (Ex). I have read that some take that as meaning they can take Summoner favored class twice each level to get +1/2 Eidolon Evolution each level. But after reading the Multitalented description, that might not be allowable. I haven't seen anywhere which says it's not specifically allowed. I think I'll agree that this is not clearly in the rules, so the way the program is currently working should be considered correct. At least you get a 1/4 point and can also get an extra hit point.