It does 1 damage because the 75% damage reduction on the cron stacks additively with the 30% damage reduction that Jabba lead gives to Hutt Cartel allies for 105% mitigation.
Damage × (1 - (0.75 + 0.3)) =>
Damage × (1 - 1.05) =>
Damage × -0.05
So realistically (with the way it's currently set up), Krrsantan would be taking negative damage, but damage has to be positive, so they set it to 1.
Damage reduction values should be multiplicative. It should be:
Damage × (1 - 0.75) × (1 - 0.3) =>
Damage × 0.25 × 0.7 =>
Damage × 0.175
Means only 82.5% total mitigation, but this is the correct value. They wouldn't ever reach 100% mitigation like this and the damage that Krrsantan receives from a hit with this cron would properly be only 25% of what he would normally take.
1000 × 0.7 = 700
1000 × 0.7 × 0.25 = 175
175 / 700 = 0.25
But I doubt it ever gets changed to work correctly.