How to get raw data from m4a file with AVAudioPCMBuffer in correct way ? Swift

Question

I try to record with an iPad and get raw data, like importing an m4a file into Audacity, the displayed waveform is what I want, but when I try to do something similar in Swift, I get wrong numbers

Here is my code: the recording part

let recordingSession = AVAudioSession.sharedInstance()
try! recordingSession.setCategory(.playAndRecord, mode: .default, options: [.allowBluetooth, .defaultToSpeaker])
try! recordingSession.overrideOutputAudioPort(.speaker)
try! recordingSession.setActive(true)
  
let filename = "1.m4a"
let fileUrl = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)[0]
            .appendingPathComponent(filename)
        
let settings = [
            AVFormatIDKey: Int(kAudioFormatMPEG4AAC),
            AVSampleRateKey: 44100,
            AVNumberOfChannelsKey: 1,
            AVEncoderAudioQualityKey: AVAudioQuality.max.rawValue
        ]
        
do {
      audioRecorder = try AVAudioRecorder(url: fileUrl, settings: settings)
      audioRecorder.delegate = self
      audioRecorder.prepareToRecord()
      audioRecorder.record()
} catch {
     finishRecording(success: false)
}

Here is my code: the parsing part

if let url = Bundle.main.url(forResource: "1", withExtension: "m4a") {
     do {
         let file = try AVAudioFile(forReading: url)
         if let format = AVAudioFormat(commonFormat: .pcmFormatFloat32, sampleRate: file.fileFormat.sampleRate, channels: file.fileFormat.channelCount, interleaved: false), let buf = AVAudioPCMBuffer(pcmFormat: format, frameCapacity: AVAudioFrameCount(file.length)){
                    try file.read(into: buf)
                    let buffer = buf.audioBufferList[0].mBuffers
                    let floatArray = Array(UnsafeMutableRawBufferPointer(start: buffer.mData, count: Int(buffer.mDataByteSize)))
                    print(floatArray)
         }
      } catch {
            print("Audio Error: \(error)")
      }
}

My goal:

after zoom in

but I got: after zoom in

Even the number of Array is much lower than the number I expect. Is there any step I misunderstood? Sorry if there are English grammar mistakes, thank you.