Estimating - Do you break large tasks into smaller tasks?
A PBI should not take more than 2 days. Each task under it should not have an estimate of more than half a day (4 hours).
If you have a big task with an estimate of more the 4 hours, you should consider breaking it in sub-tasks. In case the estimate has changed during the sprint, the “Remaining Hours” field must be updated in order to have an accurate Burndown chart.
The reason Scrum limits the maximum hours is because you should always know in which task you are working and we believe one single action that takes more than 4 hours might be too generic.