ABOOBAKER ISMAIL
Some mechanisms can be set to go off at precise times, there are others that cannot be set off to go off at precisely a particular time.  In the case of ordinary limpets, because they were dependent on the heat of something, and depending on the ambient temperature, basically because they are mechanical and depending also on the quality of the metal and different batches would differ, you would find that that would have to cut through that metal and then it would go off.  It is very inexact, but it gives you a broad range.  Often you know, there were a range within this hour to that hour.  In the case of the electrical detonators, where they were set for a particular time, they would go off within the time given.