Document link:
https://docs.redhat.com/en/documentation/red_hat_enterprise_linux/7/html-single/system_administrators_guide/index#sec-Config_ReaR
[EDIT, I had the link wrong, correcting]

Section number and name:
27.1.2 configuring ReaR

Describe the issue:
OUTPUT_URL=++file:///mnt/rescue_system/++
should be
OUTPUT_URL=file:///mnt/rescue_system/

Impact of this issue:
Customers are configuring incorrectly due to this issue.

The other rhel product docs have this part right:
Online manual for RHEL8, this example is removed.
https://docs.redhat.com/en/documentation/red_hat_enterprise_linux/8/html/configuring_basic_system_settings/assembly_recovering-and-restoring-a-system_configuring-basic-system-settings#proc_setting-up-rear_assembly_recovering-and-restoring-a-system
(See Chapter 18.1 Setting up ReaR )

Online manual for RHEL9, this example is removed.
https://docs.redhat.com/en/documentation/red_hat_enterprise_linux/9/html/configuring_basic_system_settings/assembly_recovering-and-restoring-a-system_configuring-basic-system-settings#proc_setting-up-rear_assembly_recovering-and-restoring-a-system
(See chapter 14.1 Setting up ReaR.)

Online manual for RHEL6, the example exists with correct syntax.
https://docs.redhat.com/en/documentation/red_hat_enterprise_linux/6/html/deployment_guide/integrating_rear_with_backup_software#sec-Configuring_the_Internal_Backup_Method
(See Example 34.4. Adding tar Backups )