Actually, it depends. FB will use the "Original Estimate" and this can actually change from the "first estimate". I'll elaborate:
- PM enters an estimate of 10 days. (No one has put ANY time against the case yet)
- PM assigns to Dev. (No one has put ANY time against the case yet)
- Dev changes estimate to 5 days. (No one has put ANY time against the case yet)
- Dev puts elapsed time into the case directly into the elapsed time field or via "Working On" function. 5 days becomes the Original Estimate.
- FB doesn't count something as the Original Estimate until work is done against the case.
- Once work is done against the case, the existing estimate becomes the Original Estimate (even if it's not the first estimate)
- Whoever entered the estimate that existed at the time work started, will have the case go against their EBS and history.
- This means that if the Dev hadn't changed the estimate from 10 days, EBS would be based off of the PM. Also, the developers delivery of the case (estimate vs. elapsed) would go into the PM's history, not the developer's. (This is an important distinction if you want to use EBS)
- If you have a true outlier estimate which was way off due to a typo, you can remove the data point from your history
To make sure that the developer's history is used, make sure everyone change the estimate before they start work on a case (Note this only works the first time. You can't change the estimate, start work, change the estimate again, and restart.).
To be safe, I never put in estimates before giving the case to someone. If you have to, then follow the rules above.