forgeplus-react/node_modules/rsuite/lib/InputNumber/styles/mixin.less

.input-touchspin(@size) {
  @size-name: ~'input-height-@{size}';
  @height: ((@@size-name - 2px) / 2);

  height: @height;

  > .@{ns}icon {
    height: @height;
    line-height: unit((@height / @number-input-touchspin-font-size));
  }
}