The number after Threshold is normally the percentage of damage a player needs to do to qualify for the loot listed below it, the numbers after the loot is the percentage to get the loot after qualifying percentage (threshold) is met. An example of this would be a threshold of 0.025 which means that the player needs to do at least 2.5% damage to the entity to qualify for the extra loot.
Take this with a grain of salt though, I may end up being completely wrong