Surrogate-agent multiple registration issue

Hello, colleague.

Hope you are doing good.

Could somebody advise, how to configure multiple registration on surrogate-agent if we intend to register usernames 3531, 3532 and 3533?

1) with following configuration SBC tries to register 3530, 35301, 35302, 35303:

 aor-count                              3

       auth-user                              3530

        count-start                            1

2) with following configuration it tries to register 353, 3531, 3532, 3533:

  aor-count                              3

       auth-user                              353

        count-start                            1

3) with following configuration it tries to register 3531, 35311, 35312, 35313:

 aor-count                              3

       auth-user                              3531

        count-start                            1

Second option is OK, but still we try to register first non-existent AoR "353"

Thanks and regards,

Daureen