[Marabekm]

look at the MDS guide that was with 4.10.

Here:

Craters
On this screen you can modify time before bomb/gun/rockets craters disappear. Default
multiplier is set to 1.0 for all of them. Default times are also stated (number next to text
boxes). By changing multipliers, you can make craters visible longer time. However this only
works in single player mission and coop missions. Setting long crater durations in dog fight
missions would cause inconsistency between players, since DF mode allows joining anytime.

So 1.0 is the multiplier. Changing it to 2 would make craters stay for 160 seconds (2 minutes 40 seconds), changing it to 3 means 240 seconds (4 minutes), and having it set to 9 would make crater there for 720 seconds (12 minutes), ETC.
But this only works in single missions or coops. Not dogfights.