The percentage that, in the calculation of commercial weight of textile material and of yarn linear density is added to the oven-dry weight. The determination of this weight may or may not be preceded by washing to remove natural or added oils and dressings. The recommended allowance is arbitrarily chosen according to commercial practice and includes the moisture regain. It may also include the normal finish that is added to impart satisfactory textile qualities to the material.
Textile Resource (http://www.textile.org.uk)