When authoring tests it is difficult to see if the selected test items are accurate for the give time to take the test. E.g. when a test is scheduled to take 1h, it should not contain items that requires 2h of work.
The estimated time however is only an indicative metadata field. It is not required to be filled out, so it might be empty.
The labelling must be made in a way that it is not confused with a time constraint. We do not have time constraints on question item level, only on test level.