Please help me, why is Bitcoin BTCUSDT GetDepth (()) returning only a small amount of data, not enough depth?

Binance Cash BTCUSDT GetDepth (()) returns only a small amount of data, not enough depth It only returns data between 1589 and 15885, only $4.

"Info": null,
"Asks": [{
    "Price": 15889.68,
    "Amount": 0.02221

。。。。。。。

。。。。。。。

    "Price": 15885.16,
    "Amount": 0.42772

I can't do that. I'm using get to see the results.

exchanges[1].IO(“api”, “GET”, “/api/v3/depth?symbol=BTCUSDT”);

It has been returned to Futures_OP 4: 400: {code:-1100,msg:Illegal characters found in parameter symbol; legal range is ^[A-Z0-9-_.]{1,20}$.}

It doesn't matter how big or small it is.