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You are right, I saw some blank submissions in your form. Here's a screenshot:
It is possible that some of your users or visitors did not fill up the form and just hit the submit button. It is also possible that spam bot are automatically submitting the form.
I would suggest you to insert a Captcha field in your form. Here's a guide: https://www.jotform.com/help/205-How-to-Add-a-CAPTCHA-field
You may also want to set some fields as "Required" so that the form cannot be submitted unless the required fields are filled up.
Hope that helps. If you have any questions, let us know. Thank you.