View Access Role Members / Administrators only return 1000 users. There are more members than that.
Limit on the User Directory itself.
Release : 14.x
Component : IdentityMinder(Identity Manager)
The limit for this is enforced by the user store endpoint (ie CA Directory / AD etc).
For CA Directory, the limit can be changed by adjusting the max-op-size value in the relevant configuration file
set max-op-size = 10000;
For Active Directory, the limit can be changed by adjusting MaxPageSize (1000, by default) - as explained here https://techdocs.broadcom.com/us/en/symantec-security-software/identity-security/identity-management-and-governance-connectors/1-0/connectors/microsoft-connectors/microsoft-active-directory-exchange-and-skpye-for-business(lync)/Managing-the-Connection-to-Active-Directory/active-directory-customizations/change-the-active-directory-search-limit.html
Launching NTDSUTIL.exe on your DC as explained above, the flow should be similar to this example - where the MaxPageSize was changed to 1234
We can see how post this change, number of users returned now is limited to our new MaxPageSize of 1234