WTF! Too Many (more than 4 Billion) spams in my YouTube mailbox!?

I got about 20 spam mails in my YouTube Mailbox about an hour ago, and blocked senders of those. But, Now, I found I got more than 4 billion spam mails. It seems it's not delivered to (reflected on) my mail box yet, though. (Did YouTube shut-down those? or is this just an error of the counter?)
YouTube is announcing it will get maintenance in 30 min. Is this maintainance because of the spamming?

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