An IEntityDrop refers to a drop from an Entity.

It might be required for you to import the package if you encounter any issues (like casting an Array), so better be safe than sorry and add the import.
import crafttweaker.entity.IEntityDrop;

You can retrieve this information out of them.

ZenGetter	What does it do	Return type	Usage
ZenGetter chance	What does it do Returns the chance of the drop.	Return type float	Usage drop.chance
ZenGetter max	What does it do Returns the maximum Amount of the drop.	Return type int	Usage drop.max
ZenGetter min	What does it do Returns the minimum Amount of the drop.	Return type int	Usage drop.min
ZenGetter playerOnly	What does it do Returns whether the drop is playerOnly.	Return type boolean	Usage drop.playerOnly
ZenGetter range	What does it do Returns the minimum to maximum Amount range of the drop.	Return type IntegerRange	Usage drop.range
ZenGetter stack	What does it do Returns the dropped Item.	Return type IItemStack	Usage drop.stack