Very basic here.  I'm on the import to data challenge.  I walk through all of the steps and then receive an error after I get the success email.  I'm unsure on how to correct it.  I loaded 20 records and I get a success email with 20 records.  

Challenge not yet complete... here's what's wrong: 
One of the contact records from the CSV file could not be found in the Org.

Very basic here.  I'm on the import to data challenge.  I walk through all of the steps and then receive an error after I get the success email.  I'm unsure on how to correct it.  I loaded 20 records and I get a success email with 20 records.  

Challenge not yet complete... here's what's wrong: 
One of the contact records from the CSV file could not be found in the Org.