This may be different depending on the constraints, but for a Simple
duration type and ASAP constraint, if the task is already started, then
the Estimated Due Date is calculated by taking today's date, and adding
the duration * (1-%cpt). So actually, the Actual Start Date doesn't
really matter in this case. But if you don't change the status of the
task, then you haven't changed the % cpt either because changing the
%cpt changes the status. Actual hours has no effect on the Estimated Due
Date.