ProgressCallback func params total = -1

[omitchen]

Describe the bug
I want to implement the download progress function of wasm. Through
export declare const toBlobURL: (url: string, mimeType: string, progress?: boolean, cb?: ProgressCallback) => Promise<string>;
I found that cb can be used, but the total in the callback is always -1

To Reproduce

const ProgressCallback = (event: DownloadProgressEvent) => {
    console.log("event", event);
  };
const [coreURL, wasmURL] = await Promise.all([
  toBlobURL(
    `${baseURL}/ffmpeg-core.js`,
    "text/javascript",
    true,
    ProgressCallback
  ),
  toBlobURL(
    `${baseURL}/ffmpeg-core.wasm`,
    "application/wasm",
    true,
    ProgressCallback
  ),
]);

Expected behavior
Hope to get the total value

Screenshots

Desktop (please complete the following information):

• OS: MacOS
• Browser chrome
• Version [e.g. 22]

Smartphone (please complete the following information):

• Device: [e.g. iPhone6]
• OS: [e.g. iOS8.1]
• Browser [e.g. stock browser, safari]
• Version [e.g. 22]

Additional context
Add any other context about the problem here.