Float time updates

Hi Experts,

I have a question I am hoping to get answered. When I create an activity and set the Constraints on the Dates tab (Start constraint and date, Finish constraint and date, and Early/Late) At this point the Total float appears to be set. If anything changes either a constraint or a date the Float gets set to 0. Is this normal behavior? How does the Float get recalculated? Is there any configuration that controls this?

Thanks,

Kevin