App Store offers Safari 11.0.2 which I already have Today App Store offered me Safari 11.0.2. But I already have this. See the screenshot below.

Should I just update it again? Or is there something else I can do?
Yes install it.

It's an updated version released today that has fixes for the Spectre bug that's in the news.

More information here: https://support.apple.com/en-us/HT208403