Configuring bomb craters

[stugumby]

How do i get bomb craters to stay active on a map. Im not talking about the emplaceable objects craters but from bombs dropped onto an enemy airfield etc. In the fmb there is a misc section and it has configure craters, i want to bomb gasmata field and have the craters to stay for a while, do i set a timer?? it shows a greyed out box of 80s* which i think means 80 seconds, thats why the craters dissappear?? the white box has 1.0, is this 1 hour or 1 minute?? Any help greatly appreciated.