I visited Binance's main page on BUSD [1] and it suggests you go look at their proof-of-reserves page [2], which lists the exact number of each token on Ethereum (5,334,500,000), BNB (5,315,999,056), Avalanche (11,500,000) and Polygon (6,000,000), each with links to block explorers. Note that if everything adds up, this total leaves 1,000,944 tokens on Ethereum, but at least that's positive.

Edit: I spent some time thinking the Ethereum number was the total number of BUSD, but apparently it is Binance's holdings which can be found in a wallet nicknamed "Binance: Binance-Peg Tokens" on Etherscan [3]. Since this number is greater than the total number of pegged tokens, I guess everything adds up. (Of course, since the "cross-chain peg" here is implemented in a centralized way by Binance, it could de-peg at any point they want it to.)

[1] https://www.binance.com/en/blog/ecosystem/understanding-busd... [2] https://www.binance.com/en/collateral-btokens [3] https://etherscan.io/address/0x47ac0fb4f2d84898e4d9e7b4dab3c...