How to get the actual distance of the depth map image subject from the true depth camera

I was able to obtain the depth map image using AVCapturePhotoOutput from the delegate method

func photoOutput(_ output: AVCapturePhotoOutput, didFinishProcessingPhoto photo: AVCapturePhoto, error: (any Error)?)

I convert the depth map to kCVPixelFormatType_DepthFloat32 format and get the pixel values of the depth map using the below code

 func convertDepthData(depthMap: CVPixelBuffer) -> [[Float32]] {
        let width = CVPixelBufferGetWidth(depthMap)
        let height = CVPixelBufferGetHeight(depthMap)
        var convertedDepthMap: [[Float32]] = Array(
            repeating: Array(repeating: 0, count: width),
            count: height
        )
        CVPixelBufferLockBaseAddress(depthMap, CVPixelBufferLockFlags(rawValue: 2))
        let floatBuffer = unsafeBitCast(
            CVPixelBufferGetBaseAddress(depthMap),
            to: UnsafeMutablePointer<Float32>.self
        )
        for row in 0 ..< height {
            for col in 0 ..< width {
                if floatBuffer[width * row + col].isFinite{
                    convertedDepthMap[row][col] = floatBuffer[width * row + col]
                }
            }
        }
        CVPixelBufferUnlockBaseAddress(depthMap, CVPixelBufferLockFlags(rawValue: 2))
        return convertedDepthMap
    }

Is this the right way of accessing the depth float values from a depth map. And what will be the unit for it. Because some times the depth values are in range of 0.7 when I keep the device close to the subject around 15 to 30 cm.