All it means that a device us querying pihole more that 1000 times per minute. Pretty much abusive behavior.,
Would you be able to see what device is using that IP ? is that the ASUS router?
Possibly the router is handling all DNS queries and then forwarding requests to your Pihole.
I assume that's why you see 1000 + queries per minute.
My Pihole is the primary DNS, meaning devices will query Pihole directly, and that way I can identify my Roku as the client that gets rate-limited.
This happens especially in the first few minutes after it powers on, it just keeps calling home and abusing the Pihole
Another culprit could be your PC especially an antivirus could be doing that. And of course, there are plenty of IoT devices, tablets, phones, etc that are known for calling home too often.
What is going to be really annoying for you right now is that if your Asus router is the only client for Pihole and alrady getting rate limited , than all your other devices waiting for a DNS reply from Asus will be effectively blocked for a few minutes. Pretty annoying. because they will show popups to check your internet connection and cause you to call your Internet provider 