This is a minor system update. The firmware weighs 175 MB and has been updated with the July Google security patch. It fixes some software vulnerabilities. In addition, OnePlus has fixed minor bugs in the system, as well as improved the performance and autonomy of devices.
As usual, the new firmware is being distributed in waves. If you do not want to wait your turn, then the new software can be downloaded through the Oxygen Updater application and installed manually.