Because they counted everything a conquered tribe owned, they needed a way to remember everything they had counted. They invented the quipus. The quipus had colored strings tied to a main string. The color of the strings and the distance between the knots tied in each string told a story - how many of this, and what was going on. You had to have special training to be a quipus reader.
The Inca invented a calendar they called time makers or time watchers. This calendar was tower. Time was important to the Inca for religious purposes.
They also invented a flute, a drum, the famous Inca panpipe (a collection of hollow tubes of various lengths stuck together), terrace farming, freeze dried foods, aqueducts, strange and scary art, a central government, a unified language, woven colorful textiles, gold and silver jewelry and statues, specialized professions, a system of communication (the roadrunners) and much more. They were very clever people.