When you do expedition, the 10x multiplier is applied to the reward and if before you completed the expedition, you close and re-open the game. The 10x multiplier is re-apply on the already multiplied rewards hence led to the possible million of credits/resources gained from just one expedition. I tested this by just doing that lol. I used gameguard as someone mentioned in this thread a few days ago on how to fix/reduced the amount of credits i have