Task length during drag-and-drop
 

I'm a bit confused about how visible Task length works in the Gantt view.

Say I have a task that is set to 10 hours' Effort and I have 1 resource for it set to 100% assigned amount. As I drag it back and forth in the Gantt view, depending on whether the resource is available or not, the Duration can scale from 10 hours to 12 or 15 or even 20--just depends. OK, that makes sense; and the length of the bar expands accordingly, which is fine, because if the guy (that would be me) has a lunch break in the schedule, the Duration gets longer (though the Effort is still the same).

Now, say the same task is set to 50% complete. If the Task bar in the Gantt view rests on a day when the resource for it is working a double shift with no lunch (crack that whip!), the bar is still, of course, 10 hours' Duration, because it's all going to get done. Now if I drag it somewhere else, say the Duration shifts to 20. But since the % Complete calculates from the Duration not the Effort, the percentage complete now shows up as 10 hours, and likewise the INCOMPLETE % is now 10. What's really weird about this is that I KNOW the task is half done; it only requires 5 more hours. Now I'm staring at the bar, the right half of which is the incomplete part, and it falls squarely in the afternoon when the resource definitely has 5 free hours, but because the Completion metric is scaled from the Duration metric, the program thinks the incomplete amount is 10 hours, and therefore it the program won't fit the incomplete right half into this particular afternoon.

If this because I have something set wrong? What this boils down to is that when I have a task partially completed and I drag the completion nub over to show it, I can no longer trust how many hours the incomplete portion now shows.

Any info anyone has to help me understand this would be greatly appreciated. Thanks!