Original Time Estimate not correct on Burndown chart

[Douglas LaPointe]

We add stories to our sprint, add tasks for every story and add a time estimate for every task. When we start the sprint the burndown chart does not show the correct total of estimated hours.

In this example we had 108 hours of estimated time across all of the tasks and the burndown chart started us at about 25 hours. 

If, and only if, we go into every task and in Time Tracking enter remaining hours equal to the estimate of hours does it seem to update the burndown chart. That is what we did to produce the chart above.

Why doesn't Time Remaining start off being equal to the Time Estimate?

Is there a better way to get the burndown chart to be accurate?

Here is how we are configured for time estimation.