19% chance of a moon!!

The attacker has won the battle !
You receive 108916 units of Metal, 12092 units of Crystal and 31492 units of Deuterium.
The attacker has lost a total of 0 units.
The defender has lost a total of 8.709.900 units.
A debris field containing 1.480.140 units of Metal and 421.800 units of Crystal has formed in orbit around the planet.
The probability of creating a moon is : 19 %
A moon has formed around the planet xxxxxx [x:xx:xx] !

19%? I thought the highest chance was 18%

it happens sometimes. don't know the details