for an activity with a start date in the past, when i update the status date of the project, why doesnt it increase the actual duration? because the days has progressed (i am telling this to the program by updating the status date right?) but the activity still did not finish. then i tried writing the actual start date as it was saying N/A and I just made it same date as the activity's scheduled start date. but it didnt affect it eaither.

does actual duration mean actual duration to date? or total actual duration including to date and future? is it a calculated or entered column?

by the way, where can i say if a column is a calculated or or entered column or not and if calculated the calculation formula?