Ordersell issue

The error message is as follows: 2023-02-12 16:57:58 Futures_OKCoin Error Sell ((21816.29, 5.99): map[code:1 data:[map[clOrdId:9e7f8f03cd7548BCbbc4AC5D4E708813 ordId: sCode:51121 sMsg:Order quantity must be a multiple of the lot size. tag:]] msg:All operations failed] The amount of information sold = 5.99 amountBuy = 0 2023-02-12 16:57:54 Information The amount of bitcoins that can be sold 5.99 The price of the property is 21814.890000000003 2023-02-12 16:57:54 Information The amount of bitcoins that can be purchased 0 This is a list of all the episodes of the anime series, which aired in Japan between January 1, 2021 and February 2, 2021. This is a list of all the different ways High: 21911.75 Low: 21631.4 Sell: 21816.3 Buy: 21814.3 Last: 21847.6 2023-02-12 16:57:54 information account information 0

The code is as follows:

  exchange.SetDirection("Sell")  
  exchange.Sell(sellPrice,amountSell);
  Log("账户信息",account )
  Log("账户信息",account.Balance )
  ticker1 = exchanges[0].GetTicker() // 首先读取当前行情信息，主要用到最新成交价
  Log("High:", ticker1.High, "Low:", ticker1.Low, "Sell:", ticker1.Sell, "Buy:", ticker1.Buy, "Last:", ticker1.Last, "Volume:", ticker1.Volume)
  Log("买价", buyPrice)
  Log("可买的比特币量", amountBuy )
  Log("卖价",sellPrice)
  Log("可卖的比特币量",amountSell)

I've seen the code in the forum and wanted to try it out. I have 5.99 BTC in the simulated account. Thank you.