Why would they be adding sealed docs to a warrant that has already been served? That seems very CYA.
If the DOJ/FBI filed them, could they be revising the scope of the original warrant, to cover everything they took that wasn't included in the original warrant? If that's the case, it's very reminiscent of A.G. Rod Rosenstein revising the scope of investigation memorandum twice after the original was written, in order to cover Mueller's continued fake Russian collusion investigation.