The JIRA API has (at least) four fields exposing time tracking data. In the jira-python python wrapper, these are exposed as follows, assuming you have a local variable
issue containing an issue object.:
aggregatetimeestimate track the "Remaining" time left on the issue.
aggregatetimeoriginalestimate track the original "Estimated" value.
Although I have not tested it, I suspect that the
aggregate variables contain the sum of all subtask estimates. For normal tasks, they seem to always equal the non-aggregate fields.