Can a officer only seize what is on the search warrant?

No, an officer can seize items that are not specifically listed on a search warrant if they are in plain view and the officer has the legal right to be in that position. Additionally, items that are evidence of a crime, contraband, or otherwise illegal may also be seized even if they are not mentioned in the warrant. However, the scope of the search must still adhere to the limitations set forth in the warrant.