What does the contingency percentage in the results actually cover?

Contingency is meant to absorb latent soil issues discovered during excavation, mid-build decisions such as a layout tweak, and the ordinary variation that happens on almost every real construction site. It is not designed to be a contractor profit margin dressed up as risk cover, and an honest estimate keeps it as a visible, separate line rather than folding it invisibly into the headline rate. If you spend the contingency on upgrades early in the project, you may have little left to absorb a genuine site surprise later.