If you increase your /players settings, it increases the chance that the Countess will drop more items in her first item-drop. Combining these two drops, the maximum number of total items she can drop at one time is 6.
The second drop-check that occurs is her special rune drop. The first drop-check that occurs is a (mostly) normal item drop, which is why she likes to throw Town Portal scrolls all over the place when you kill her. Without getting too in-depth, basically the Countess has two item-drop-checks. The reason is how the Countess drops items: Do not run the Countess on /players8 if you want to collect runes. In Single-Player, that means using /players1 exclusively. Essentially, you want to minimize the number of other players in the game.
