Improve how capacity consumption calculations are performed

module/documents/Item/GenericItem.mjs

@@ -1 +1,12 @@
-export class DotDungeonItem extends Item {};
+export class DotDungeonItem extends Item {
+	get usedCapacity() {
+		let capacity = 0;
+		if (this.system.uses_inventory_slot && this.system.quantity > 0) {
+			capacity++;
+		};
+		if (this.system.quantity_affects_used_capacity) {
+			capacity *= this.system.quantity;
+		};
+		return capacity;
+	};
+};