Why should the shuteye be adjusted before the detection threshold?

Adjusting the shuteye will overcome any early detection times due to matrix interference from an acidic product or CO₂ produced by a product with a starter culture (i.e. yoghurt). Increasing the threshold will make the test less sensitive as this means that the optical units will need to increase more for a detection time to take place. Decreasing the threshold would make the test more sensitive for detecting organisms that are slower growing i.e. moulds.