Stick mark is a dark band across the flooring element of approx. 20mm wide, more commonly seen with light coloured timbers such as Maple, Ash etc.
Stick mark is caused whilst air drying or kiln drying on stacking strips used to allow air to circulate between the planks of lumber, before being machined into flooring.
Sticker stain is usually allowed in rustic grade flooring.
Sticker stain usually fades with consecutive sanding, but is unlikely to disappear unless it is already very faint. If this feature is unacceptable to the end user, defect cut or set aside as waste.