Delayed YouTube keeps a YouTube player at the position you expect. Use live mode for a delayed live stream, or video mode to play a normal video as if it started at a local clock time.
YouTube playback can jump after buffering, network fluctuations, browser refreshes, or player hiccups. In live mode, that can skip the delay you were trying to preserve. In video mode, it can move away from the position that matches the video start time. Delayed YouTube monitors the player and seeks back to the expected position.