The Ignored Field Report tells you how often the fields in your form are not engaged with. This means that the visitor made no attempt to fill it out, and it was submitted to your form blank.

Like the Fill Report, the numbers in this report are calculated out of the people that engaged with the form, not out of the total number of people that saw the form. This is to make sure the report provides more data than simply the conversion rate of your form, since the conversion rate would drown out the signal for this report.