Loot Tables have a percentage (1 to 100%) to activate a Loot Drop, can be any value and doesn't interfere with the other Loot Drops.
Loot Drops have a percentage (1 to 100%) to drop a set number of items (specified in the Loot Table). The values need to all add up to 100% total.
I have tried adding say 15 items to a loot drop table and leaving their percentages at 100 and there was a huge bias towards certain items (like 10-20 drops to 1 of the other items).
Hope that helps!