On the download page, you will see:

Minimum 8 GB (16 GB highly recommended if running WinCC Professional simultaneously)

If you already have a base installation of TIA Portal V13, you do not need to download a massive, multi-gigabyte standalone ISO file. Open the utility installed on your PC. Refresh the available updates catalog.

: Allows for more dynamic programming in Ladder logic, which was previously a major hurdle for developers.