RESOLUTION
To configure the number of backup, please login to PIM and go to Backups area. There you can configure Number of Backups Available From Parallels Power PanelAlso it could be done through Parallels Management Console:
1. Open PMC, make sure that the node is registered in native mode,
To make sure please click on the node, there should not be the following massage in the right pane of PMC:
"The Virtuozzo software on this Hardware Node has been upgraded to version 4.0.0. To get access to new Virtuozzo 4.0.0 management capabilities, please reregister this Node in Parallels Management Console."
2. Then right click on the Node, Tasks, Manage Parallels Agent Configuration
3. By expanding configuration tree as backupm, configuration, backupm_config you will find pe_backups_limit value that is the number of allowed backups per container.