Dust positions are very small balances that can't be sold on Binance. You can convert them to BNB directly from Cryptohopper using the Wallet Scrubber, available on both the Dashboard and the Advanced Dashboard. Binance also has a built-in feature called 'Convert dust to BNB'.
On the Dashboard
Go to Current Assets and then select Wallet Scrubber:
On the Advanced Dashboard
Go to Current Assets, click the $ sign, and then select Wallet Scrubber:
Why isn't the entire position sold on Binance?
On Binance, trading fees are always charged in the asset you receive. For example, if you buy ETH/USDT, the fee is paid in ETH. If you sell ETH/USDT, the fee is paid in USDT. Binance also applies a minimum movement in the amount of the currency you're trading. Because of this, dust positions will occur.
There's unfortunately no way to prevent dust positions from occurring. However, you can use the Pick up leftovers feature in the Wallet Scrubber to manage them.