QUESTION:

"I have so many duplicate ingredients. Is there a way to delete them? "

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ANSWER:
There is a way to fix this problem that you're having. Unfortunately it is not a quick fix.
In Cook'n on your computer, click View->Ingredients. After that, simply select an ingredient that has the [duplicate 1] in the name and then; in the box next to "Ingredient Name" on the right hand side, remove the [duplicate 1] from the ingredient name and click "Save".
It will then ask you to replace it with another one on the list, click "yes".