There are a few reasons that you may see a discrepancy between the number of contacts in the file you are importing and the numbers as shown at the end of the Import process and in your Contacts section, or under the Recipients step.
Your original database file may contain bad records, such as invalid email addresses. After the Import Contacts process has completed, you will be able to export any failed records to review them for any errors. There may also have been duplicate email addresses in your original database file. The system will only allow one contact per email address.
A smaller number of contacts will be added to a campaign than what is displayed in the Contacts section if some contacts were already classified as opted out or bounced (in which case they are not added to the current campaign). To check to see which contacts were already classified as opted out or bounced, refer to Advanced Search.