How to get variance and progress in Time Tracking Report?

There are two columns variance and progress in Time tracking Report, how to get the data for variance and progress? Is there any formula?

Answer

Original Estimate is initial estimated time specified in issue field. Note, the field is not available in Next Gen projects, so the column is always empty for Next Gen project issues.
Est. Time Remaining is current estimation in Estimate field. It is reduced when work is logged on an issue, and may be increased as well if there is more work needed.
Time Spent is sum of worklogs for an issue, during period. Note, there is Jira issue Timespent field also, which is overall value of time logged for an issue.
Estimate = Time Spent + Est. Time Remaining.
Variance = Original Estimate - Estimate.
Original Estimate Remaining = Original Estimate - Time Spent.
Progress is Timespent / ( Est. Time Remaining + Timespent), so it's 100% when Est. Time Remaining is 0.

All columns may present summed values, if Sum Sub-Tasks is on or Group By option is set.