The Depth model is based on AMM model, which is common in the DeFi world. In all AMM models, there could be a impermanent loss caused by price fluctuation. It is called impermanent loss because as long as the token's relative price goes back to its initial state (when user provided liquidity), the loss will disappear. If users withdraw the liquidity before the ratio in the pool return to the initial state, the loss will become to be a permanent one.