remaining duration not getting updated in CN48N report

Dear All,

I have partially confirmed one of internal activity. Details as below.

Normal Duration - 10 Days (which is maintained at internal activity scheduling sub screen)

Actual Duration - 4 Days (actual duration partially confirmed through tcode CN25)

Remaining Duration - 6 Days (This must be reflected in CN48N report as remaining duartion=Normal Duration - Actual Duration)

When i see CN48N report system dosen't show Remaining Duration as 6 Days, that field is showing as blank.

Why system is not updating remaining duration field in CN48N report. Any thing is missing from my side kindly give your valuable input.

Thanks & Regards

Sandeep