Rust near both lower corners of windscreen

So 1969 Fury III convertible, I hadn't noticed this until I happened to have the bonnet up and the doors open at the same time while replacing the door jamb switches.

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Is this a common rust point and if so how depressed should I feel? For now, I got a long brush and painted some Ku-rust in there - but I prefer to get things done properly. Added an image under that area from inside the fender / door...

Rust near both lower corners of windscreen
Author: system11