This happens because Salesforce has a 2000 contact or lead limit view and MonsterConnect will only import the records that can be viewed in Salesforce.  To import all the contacts or leads, you can do one of the following:

  1. If you are importing SF leads, remove the closed records to make your list smaller
  2. Break the list into 2 lists. Use an arbitrary parameter, like contacts last name that start with A to M and then N to Z
  3. You can export your Salesforce list and import as a Salesforce CSV. 

Note – make sure you import and sync to Salesforce, rather than import as a regular CSV file.  When you import as a Salesforce CSV, the list does not automatically add and remove contacts when you make changes in Salesforce, you would need to re-import the exported Salesforce CSV.