PERI stakers can stake their PERI and receive rewards. But by staking, they also take on the risk of 'debt.' When someone stakes their PERI, to then immediately unstake it they need to burn as much pUSD as they just minted — this pUSD figure is their debt, and all PERI stakers' debt is pooled together (with each staker holding a proportion of it). But this pooled debt is also where profits and losses from people trading on PERI.Exchange is represented, so a staker's debt can change over time depending on traders' overall profits and losses. This is the risk they assume when staking their PERI.