Cashing in 2 groups of spoils during a single turn

Am kinda new to this game and picking things up as i go along. It took me a few turns to understand the spoils. Am in a game at moment and red who was not in a really strong position cashed in spoils at the beginning of their turn. Red then eliminated green from the game and then cashed in a second group of spoils and attacked me. Red has now got 41 troops sitting on my border, when most she had at beginning of turn in any one region was 6 troops. It kinda thrown me!! I was expecting red to cash in spoils as they had 5 spoils in hand. But gaining almost 50 troops in one go??? So question is how can it be possible to cash in 2 groups of spoils in same turn. And how many troops do you get when cashing in, it kinda differs from one go to next.