By credit I assume you are talking about the DEC Liquidity Pool airdrop points which as per Splinterlands doc site is 2x DEC value in the pool, now to liquidity pool is one token pegged to another and so in SWAP.HIVE:DEC pool I add DEC and SWAP.HIVE, now when people swap tokens based on which is being swapped more the value of those 2 tokens change over time resulting in imbalance or difference from what was originally added which is called impermanent loss in liquidity pools, a simple search will give you lots of article with good information to understand about the same
Again I am in no way a Financial expert this is just from experience