How is Assignee list populated in Fortify JIRA Integration


After fortify SSC JIRA integration, when we tried to file a bug , we could see few fields populated .

In the Assignee field, we could see only few names populated starting with A . So could not assign the JIRA to the right person.

we have checked with our JIRA team but they are not enabling any filters .

And this list of users being shown in Assignee list are not present in the LDAP user list as well. Then why only few users are shown while trying to file JIRA? 

Is there any filter to be checked in SSC?

Please suggest.