The knotted cords known as "quipu" or "khipu" were always constructed according to the same system. On a main line there were secondary lines attached, which could run down and also up. To these, in turn, other cords were sometimes attached. The lines themselves had knots tied into them, which represented higher values the closer they were to the main line. The Incas also used the decimal system. So the knots represented tens, hundreds, thousands or tens of thousands of units. Possibly even higher values were recorded. The Incas documented with the "quipu" numbers like tribute payments and censuses but also narratives or ruler genealogies. In order to record different things in the "quipu", different colours and knots were used. We now understand how to read the numbers and their hierarchies. However, we still do not know what the documented figures were about.