When an issue is marked done but the time has not been logged, how does this effect the chart?

[Sandrela Bahnam]

When reviewing the Burndown chart for a Sprint we have customized our board to utilize the estimation statistic-Original time estimate and the time tracking is set to Remaining estimate and time spent. I would like to verify with JIRA if the time is not logged but the issue or a sub task is marked done how will this effect the burndown chart? Does the time need to be logged in order to reflect accurately?

Thanks,