SolidWorks 2012

I designed a U-clip, 25 mm wide, thick 1 mm, using an edge flange (blind 20 mm, outside) on each side.

I now want to verify the folding of one side under different angles, so I edit the properties and increase the angle from 90 up to 180° to see what distance I get when folding up to 180.

Strange enough the flange length changes when doing this.

What am I doing wrong. Why does the flange length 20 change dramaticly when getting over 150-180°?

Thanks, Gerard