The second PS4 system software update is out now, and due to Sony’s rather unconventional naming scheme, it’s known at update 1.51, after the first huge update being 1.5 – presumably bigger updates are now worth a whole 0.5, while smaller updates such as this have a weighting of 0.01.
Moving on from discussion about naming systems and to what the update actually brings, the “minor” update offers further stability of the system software and minor refinements to elements of the UI, including a now clear distinction when players download a game and a game patch at the same time.
It should also download overnight, as automatic downloads for firmware and game updates are enabled by default when the PS4 is in stand-by mode. The size of the update is 323MB.
Source: PlayStation Blog