User able to extract Custom report other then His/her access

Summary:

We have created a custom report and we have given access to the users to extract those report. The user should be able to extract the accounts to which they are having access. But the user when tries to generate the report they are able to access all the reconciliation which is available in the system.

How can we restrict the users to see only the specific reconciliation which are assigned to them in the report?

Is there any specific security needs to be provided?