It was an recently inconceivable 7.3 Tbps:

The overwhelming bulk of the assault was executed via User Datagram Protocol packets. Authentic UDP-based communications are employed in particularly time-critical interactions, such as those for video streaming, gaming software, and DNS queries. It accelerates exchanges by not formally establishing a link before data is conveyed. Unlike the more prevalent Transmission Control Protocol, UDP does not wait for a connection to be established between two systems through a handshake and does not verify whether the data is accurately received by the other entity. Instead, it promptly transmits data from one device to another.

UDP flood assaults transmit extraordinarily high quantities of packets to random or designated ports on the target IP. Such deluges can saturate the target’s Internet connection or inundate internal resources with more packets than they are able to process.

Since UDP doesn’t necessitate a handshake, assailants can exploit it to inundate a targeted server with torrents of traffic without first securing the server’s consent to initiate the transmission. UDP floods generally dispatch vast numbers of datagrams to multiple ports on the target system. Consequently, the target system must return an equivalent number of data packets to signify the ports are unreachable. Ultimately, the target system collapses under the pressure, resulting in legitimate traffic being obstructed.