I've been investigating this with WF support a lot. Here is explanation I got:
After further investigation, it was determined that there could be up to a 3-minute variation for the planned hours within the Workload Balancer. That would explain why some planned hours don't wholly align when looking at the task details.
As an example, let's say we have a 3-day task with 10 hours. By default, the hours are equally distributed with 3.33, 3.33, and 3.33. If we were not to allow a 3-minute variation, the user would have run into an "hour sum doesn't match task planned hours" warning when the user entered the inline edit mode.
There was a separate problem with task set to 0 planned hours, but still showing up as 0.02, but I believe this has been patched
Best
Rafal