Zoho CRM integration criteria on duplicates

Dear sir/madam,

I have a question about the duplicate check function in the Zoho CRM integration. There are two options: Update Previously Added and Doesn't Add Contact if it Exists. I would like to know on what basis this duplicate check is done? Does it look at the Full Name, the Email address or some other criteria when deciding whether to update an existing record or to create a new one?

Thank you in advance. 

As I run the test with simple fields on my JotForm, I notice that the contact is being updated based on the email address. So, email address would be the criteria is the email address. If there is no email address on the form or not mapped with Zoho CRM, it automatically creates new contacts.

Hope this information helps! 

Thank you Kiran, it does!