hi, its not clear from your question if the contra charges are for matters connected with not completing by the Completion Date or for separate matters.
As Neil says, X7 is a pre-agreement for a charge to be applied in the event of "being late".
I would see X7 as the Subcontractor's sole remedy for you being late "under the terms and conditions of this Sub-subcontract".
If the contra charges are for other matters not connected to "being late" then presumably they are covered by compensation events (negatives) for changing your obligations, eg where the Subcontractor has provided labour for your use. If they are for other matters then they would be in addition to X7 damages.
As Neil says, X7 is a pre-agreement for a charge to be applied in the event of "being late".
I would see X7 as the Subcontractor's sole remedy for you being late "under the terms and conditions of this Sub-subcontract".
If the contra charges are for other matters not connected to "being late" then presumably they are covered by compensation events (negatives) for changing your obligations, eg where the Subcontractor has provided labour for your use. If they are for other matters then they would be in addition to X7 damages.