fix: use explicit Number() instead of unary plus

[RoPP]

Probably not important for the experienced js developers but it's more readable for newcomers (at least for me!).

[googlebot]

Thanks for your pull request. It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

📝 Please visit https://cla.developers.google.com/ to sign.

Once you've signed, please reply here (e.g. I signed it!) and we'll verify. Thanks.

---

• If you've already signed a CLA, it's possible we don't have your GitHub username or you're using a different email address. Check your existing CLA data and verify that your email is set on your git commits.
• If you signed the CLA as a corporation, please let us know the company's name.

[RoPP]

I signed it!

[googlebot]

CLAs look good, thanks!

[jkuri]

Hi @RoPP, thank you for the PR. LGTM.

[filipesilva]

lgtm as well, thank you!

[angular-automatic-lock-bot]

This issue has been automatically locked due to inactivity.
Please file a new issue if you are encountering a similar or related problem.

Read more about our automatic conversation locking policy.

_{This action has been performed automatically by a bot.}