A role records demand before you choose a person. Specify its project, required skill and proficiency, minimum grade, dates and weekly hours. Location is an additional constraint when the client needs someone in a particular office. Without clear requirements, a search can produce a plausible name that can't deliver the requested work.
Dates in Desk Staffing are Monday-starting weeks, with both endpoints included. Twenty hours from January 4 through January 25 means twenty hours in each of four weeks. The hours field isn't a total for the whole assignment. A pipeline role also has a probability used in weighted demand forecasts; changing that probability doesn't confirm a booking. Record a scope change on the role first, then review whether the existing schedule still covers it. Don't lower a proficiency requirement just to make a preferred person appear eligible.