What is the unlabeled percent value on a plan's progress bar?

The progress bar on a Plans page and on the Team Details section of a team dashboard shows an unlabeled percentage at the right end of the progress bar. What does that represent? It isn't the percent estimated, which is labeled "Estimated:" on the progress bar in the Plan Details section of a plan. I don't see any combination of values in a plan that comes out to the percentage shown. It doesn't correspond to the height or the length of the progress bar.

I was unable to add images to this question, so here's my attempt at showing a progress bar with text. The # characters indicate the dark green section of the bar, the '=' characters indicating light green, and the remainder of the bar white. It is the 85% figure that I'm asking about.

[#######==                         ]
175.75/428.75hrs                    85%

This text shows in the popup when you hover over the progress bar:

Progress Report
Hours Done: 175.75 of 428.75 (41%)
Expected Hours: 134 (Ahead by 41.75hrs)
Items with 'Hours': 97%
Items Completed: 36 of 149 (24%)

Those are actual values from one of our plans, RTC 4.0.7. That progress bar appears in the Team Details section of the team dashboard, and on the Plans page where all plans are listed. The same progress bar appears in Plan Details section at the top of the plan, but instead of the unlabeled 85% it shows "Estimated: 97%".

Thanks,
Greg