Try going into your skin.ini, and adding/changing a line called "HitCircleOverlap" under the [Fonts] section (If there isn't a [Fonts] section, just add one). Set it to the width of your SD hitcircle numbers. So, if your default-1.png is 200x200px, set HitCircleOverlap to 200 so it would be "HitCircleOverlap: 200". If your
default-1@2x.png is 400x400px, divide those numbers in half and use those new numbers because the HitCircleOverlap works based on an SD resolution while your
default-1@2x.png is an HD file.