Progress bar

Hi, I have a question about progress bar.

Regarding progress bar, I can find 2 different explanations as quoted below.

(1) http://jazz.net/projects/rational-team-concert/features/apt
>So if the past work time is 9 hours and you completed work you had estimated at 3 hours, the projection assumes that you'll need three times as much work time as estimated for the work that remains. Comparing the projected value to the remaining work time lets you know whether you are ahead or behind your target. The same projection is done for product backlogs using story points as the sizing attribute.


(2) http://jazz.net/library/presentation/19
RSDC2008_SDP24_DirkBaeumer.pdf :
>Resolved work: 9 hours / Total work: 11 hours
>Spent work time: 17 / Total work time: 96
>9 - 11/96 * 17 == 2 hours ahead

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My question is, which logic is correct ?

For example, if the situation is:

- Resolved work: 2 hours / Total work: 8 hours
- Spent work time: 8 / Total work time: 16

in case (1):
- remains: 6 hours
- the projection assumes: 6 * 16/8 = 12 h
- emaining work time: 8h

8 - 12 == 4 hours behind

in case (2)

2 - 8/16 * 8 == 2 hours behind