8c597b5375
this is the mapping between the half of each percentage intervals and
the associated usWidthClass:
{56.25: 1,
68.75: 2,
81.25: 3,
93.75: 4,
106.25: 5,
118.75: 6,
137.5: 7,
175.0: 8}
Notice how wdth=80 (in the adjusted test case) will fall in width class
3, instead of 4, because it is < 81.25, thus closer to the nominal 75
than to 87.5.