Using New function REGNewPerson

I am trying to use REGNewPerson introduced in Lotus Notes C 7 API. I am successfully able to create the user, with following attributes →

FirstName = user

Lastname = user

BUT the fullname field in person document is not set correctly. According to me fullname should have two values

FULLNAME = user/pspl

               user

BUT fullname has only one value.

FULLNAME = user