How to solve my Field mapping problem during import of Registration codes?
Preparing your cvs file
First remove all the column names from the first row, otherwise they will be added and will throw an error, as they won’t be in the correct format.
Drupal Regcode import tab
You can map to the following six fields:

begins: When code should be active from in date format
expires: When code should expire in date format
code: The registration code text format (for numbers and letters) and should be unique
is_active: Whether the code is active text format ‘Yes’ or ‘No’ Default is Yes
maxuses: Maximum times the code can be used number format default is 1
uses: Number of times the code has been used number format default is 0

If your cvs file codes are in the first i.e column one (A) then you would map it as code and if the next column is maximum times the code can be used then you would map as code, maxuses separated by a comma. Note: no colons.