In order to get a 100px corner, I need to enter a radius of 98 into the Round Corners. Likewise a 200px corner requires I enter a radius 196.
However if I copy the setting using the cog menu and add the Round Corners as a Custom Parameter Filter I get a different result. If I export an OTF the values are different. A CP value of 98 creates a 98px corner. Is this a bug?