Liquidity Pools unclaimed Rewards

I have provided liquidity to several stable-coin pools on Binance, for example BUSD/USDT. Now, I am seeing unclaimed rewards of 0.6178 USD in the 'My Share' overview, but the individual pools list unclaimed rewards in BNB such as 0.0005 BNB. Question: which of the denominations is authoritative? If the dollar amount was authoritative, it would make sense to wait until BNB is low and only then claim the rewards (because the fixed dollar amount would be converted into more BNB). If the BNB denomination was authoritative, then it wouldn't make any difference and I honestly don't understand why I have the option to decide when to claim rewards.

Apologies if this has been asked before.

Edit:
I might be able to answer the question myself, because I have just noticed that the USD amount of unclaimed rewards does not only grow but also sometimes shrink. That would mean that unclaimed rewards are stored in BNB.