Need help with editing a recipe

[Kibocca]

This is my first time using this forum, so please let me know if I've made any mistakes.

 

I'm trying to create a mod that edits the cobblestone recipe in the game but I keep receiving this error, and I'm unsure why. Please bear in mind that I am not super familiar with coding, I apologize if this question has a simple answer.

 

Also, I can't figure out how to override how many items you get from crafting a specific recipe. For example, if I want to change the yield of crafting Cobblestones to 4 each time you craft it instead of 1 (I hope that makes sense).