Importing a story with estimates doesn't take over the exact estimate in portfolio

We have a scenario that regularly occurs here in our workflow with JIRA portfolio.

Something to know: 1 day here is equal to 7.5 hours. In JIRA portfolio we show the estimate based on days.

An example:

1. A developer creates a JIRA ticket and estimates this, f.e. 2h
2. The story is imported in JIRA Portfolio
3. We update the plan on a daily basis as the developer fill in worklogs on a daily basis

However, when we import the story in JIRA portfolio that already has an estimate of 2 hours, the estimate shown for that story in JIRA portfolio will be 0.3 days, while when clicking on the progress we do see 0.26666... days.

All this is not so problematic, BUT, when we update the plan, JIRA Portfolio wants to update the remaining estimate in the linked JIRA ticket, while no work was done for that ticket yet. Developers then get a notification that f.e. 15 minutes were added to the original estimate of the ticket.
The plan update thinks 15 minutes were spent, and augments the original estimate with 15 minutes.