It turns out to be a handling fee. Binance said there is no handling fee, but then they deduct it. Isn't this deceiving? I get deducted even when I open a margin position. I was thinking it should be a fee, but now I understand.

Contract $BTC , opened with 600U, why did the order only give 574.42U, a direct shortfall of over 25U, asking knowledgeable experts to reply to me, I want to ask Binance customer service, but I don't know where to find Binance's customer service.