The value of your crypto has been changing, which does not mean that the number of your crypto is decreasing. This is caused by the difference between the converted price and the actual price when you buy and sell. It fluctuates according to the real-time market.
If you buy 1,000 USDT on Huobi P2P, the current unit price of USDT is 6.5, and you’ve paid 6,500 RMB. Right after you brought the 1,000 USDT, the current USDT reference price is 6.48 according to the real-time market, then the total crypto of the OTC trading account at this time is 6,480 RMB.
This does not mean that your crypto is reduced, because the quantity is still 1,000 USDT, but the total value displayed for the converted crypto is reduced due to the reference price.