Tx broadcast failure

Hi,

I’m getting a bad request response when broadcasting a tx

code: 400
failed_tx_index: 0
message: "19992500BNB < 400000000000000BNB"

The endpoint https://dex.binance.org/api/v1/broadcast?sync=true is being hit by the BncClient from @binance-chain/javascript-sdk on the transfer function with params:

from address: bnb194zzjrnuf6vnc50rcguz8746artp89t5mm0uez
to address: bnb1yah2afyktr8n2wdpm4qeu5r9r55sft2n7jwfay
amount: 4000000.0
asset: BNB
memo: =:BNB.BUSD-BD1:bnb194zzjrnuf6vnc50rcguz8746artp89t5mm0uez:971303331:t:0

Any ideas of what could be wrong in what I’m doing?