On Open Shifts, the Signups column shows "n signed up". Click it to open Employees Signed Up, listing Employee, Email, Signed Up (date/time). For an open request, each row has an Add to Schedule button: clicking it creates a real shift for that employee with the request's date, time, role and color, and sets the request to Filled. If the employee already has an overlapping shift, the usual overlap error appears and nothing changes. Other signups stay listed but can no longer be added, and they are not notified automatically.