Basic method for updating the progress rate 

Click % Done to open Edit mode. Then you can either click the up/down arrows or directly enter a value.

However you cannot edit the progress rate for:

• A project or version
• Issues in gray color

Auto-calculating parent issue progress rate 

You may want to synchronize the progress rate between parent and child issues. This would mean, for example, that when the progress rate of a child issue is 100%, the parent issue's progress rate will also be 100%. You can do this with Auto-calculate percent done.

To use this feature, you need to enable Auto-calculate percent done in user preferences. For more information on user preferences, refer to this document.

The calculation of the progress rate is based on time spent and duration. For instance, if Issue A has a duration of one day with 100% done, and Issue B has a duration of two days of with 50% done, the total parent issue progress rate would be:

(100% * 1 day + 50% * 2 days) / (1 day + 2 days) = 66% (Decimals are rounded down)

As shown in the progress bar, the one day issue has 100% percent done with all work for the day completed. The two day issue has 50% done, with one day's work completed. Therefore, for the parent issue, two days out of three are completed, equating to 66% done.