: "05" likely refers to a specific clip number or a "piece" of a larger recording session.
: Since it is a .zip file, it is a compressed archive. It might contain the video file along with metadata, such as a log or thumbnail, or it could simply be a way to save space on a larger collection of clips. Rocket League 2022.09.30 - 01.23.59.05.DVR.zip
In the context of DVR and video files, "piece" usually refers to one of two things: : "05" likely refers to a specific clip