The way raid bases generate loot is each difficulty has a set amount of "loot" it generates. So let's pretend that is '50 items' just for an example. We have an extensive loot table the plugin can draw loot from. Higher difficulties have better stuff in their table, of course. And some items (resources for example) have a min/max amount too. For example if the configured table has 1,000 to 10,000 stone, you could get anywhere in between those values but that stack of stone counts as one loot item.

So if a base is meant to have 50 pieces of loot, the plugin rolls the dice 50 times and picks an item from the loot tables for each random roll. Then the plugin auto sorts that loot distributing it evenly among all the boxes in the base. If any of the loot happens to be resources or anything that can go inside a TC, it will sort those into the TC of the raid base rather than a box.

But keep in mind, as said earlier, you may not even get "resources" from the random loot rolls. If that's the case then the TC would be empty (and might be better for you since that means more chances of random loot being boom or guns).

Higher difficulty bases of course have a much better chance of the TC not being empty since they generate a LOT more loot than lower tier bases do, which means more chances for that loot to be resources or something that can go inside a TC.