rounded corners become pointy from PS to Web

[patent10021]

I rounded the corners in PS then uploaded to hosting.

1. Why did the corners become boxy/pointy?

2. Both the radius of the image and radius of the outer stroke are 65px but the white space at the sides appears different than the white space at the corners. The canvas is 30px larger than the image. I thought I would need to compensate with some math but none of the numbers worked.

 

[organicCPU]

Shouldn't be there a difference of the inner and outer border's radius by the amount of pixels equal to the distance of those two lines? E.g. outer radius 65px, inner radius 60px, if there were 5px distance. For more complicated things: https://en.wikipedia.org/wiki/Parallel_curve

I usually design in resolution by the factors @2, @4 or @8 of final output size to keep impact of Photoshop's anti-alias rendering bugs as small and quality as high as possible.