The problem sounds like how you are making these ... you are making 1 Option Name per selection ...

You need to make 1 Option Name and then add the Option Values to that ...

Option Name Manager ...
Option Name: Size
Option Type: Radiobutton

Option Value Manager ...
Option Name: Size
Option Value Name: Small
Sort Order 10

Option Name: Size
Option Value Name: Medium
Sort Order 20

Option Name: Size
Option Value Name: Large
Sort Order 30

Attributes Controller ...
Option Name: Size
Option Value: Small

Option Name: Size
Option Value: Medium

Option Name: Size
Option Value: Large

When done adding them, hit Update Sort Order ...