He's using <a console command to get a random number> to spam those messages. I thought this wasn't possible, but I guess Blockland's spam protection isn't as good as I thought.
/support
If I am correct, the default message function just checks if the last message is the same as the next, and if the time period is long enough before flagging the person as spamming.
Other than that it doesn't check anything else at all.
Though, some chat mods will break this spam protection, making it easy as hell to spam servers.
Anyway, the best protection for spam is an activate administrator team for your server, especially if it's popular.
Otherwise there will always be ways to work around the spam protection.
Even though that wouldn't work on majority of servers, I wouldn't have posted that if I were you.