on
n Function
0 Underline off
1 Set underline thickness to 0.125mm
2 Set underline thickness to 0.25mm
3 Set underline thickness to 0.375mm
4 Set underline thickness to 0.5mm
5 Set underline thickness to 0.625mm
6 Set underline thickness to 0.75mm
7 Set underline thickness to 0.875mm