In timeboxed iterations, you have to be very careful that work doesn't expand to fill all available time. If you are a little conservative with your estimates,

In timeboxed iterations, you have to be very careful that work doesn't expand to fill all available time. If you are a little conservative with your estimates, its easy to double the time the necessary aspects of development would take. Little, unnecessary tweaks becomes more important than putting four hours into the stretch goal that is going to spill into the next sprint. Six times is a bit much, though. That sounds like they haven't worked out their estimations yet.