Why are there multiple Time Tracking fields choices in the Column Chooser in Issues Search?

[Allan Flatoff]

On the Issues Search page in JIRA, when using the Column Chooser, there are duplicate options for the "Time Tracking" fields of:  Original Estimate, Remaining Estimate, Time Spent.

One of the versions of each field has the "Sum" icon by it.

We haven't seen any difference in the values produced by either field.

So. . . why are there two different versions of each field (Sum and Regular), and what is the difference, if any? 

image2017-2-6 11:37:41.png

[Nic Brough -Adaptavist-]

Original estimate will give you the estimate for the issue on that line.  Ths sum will give you the same field, but for the issue and all its sub-tasks.