Incorrect Original Estimate after CSV Import

Summary

Using JIRA's CSV Import feature, when user import a CSV file with default time tracking time set to anything other than minutes, JIRA displays wrong value for the estimated time. This issue can't be reproduced if the the CSV import is done using the External import feature.

Environment

JIRA 6.4.12 -> JIRA 7.0.5

Steps to Reproduce

1) Import a CSV file with the following content:
Summary;Fix Version;Original Estimate (in seconds);Issue Type
issue 1 (estimated 8h = 1d);1.2.3;28800;Task
issue 2 (estimated 40h = 5 d = 1w);1.2.3;144000;Task
issue 3 (estimated 2h = 0.25 d);1.2.3;7200;Task
issue 4 (estimated 15' = 0.25 h);1.2.3;900;Task

2) Open the Issue navigator to see the time tracking value

Expected Results

independent from default time tracking unit the result should be
issue 1: 1d
issue 2: 1w
issue 3: 2h
issue 4: 0.25h

Actual Results

(time tracking set to day)
issue 1: 0d
issue 2: 1d
issue 3: 0d
issue 4: 0d
and if default time tracking is set to hour:
issue 1: 1d
issue 2: 5d
issue 3: 0.25d
issue 4: 0d
and if default time tracking is set to minutes:
issue 1: 1d
issue 2: 5d
issue 3: 0.25d
issue 4: 0.25h
and if default time tracking is set to weeks:
issue 1: 0d
issue 2: 0d
issue 3: 0d
issue 4: 0h

Workaround

Importing for External Import function will import the CSV file with right time tracking value.