Expected Remaining unit / time to be Zero

Hi , 

I recently updated an actvity as completed , and accordingly have remaining duration and remaining units as zero.

Howvever in resource tab , for the same activity i have remaining uint/ hr as 1  eventhough remining units are zero.

I was expecting even remining unit/ time as zero since there is no more to spend on that actvitiy.

Hope some one can throw some light on this.

Thanks in advance,

Vinod Raturi