how to use meters?

["Kamil Jońca" <kjonca@op.pl>]

I try to understand "meters" and I have an impression I missed
something.
Use case:

--8<---------------cut here---------------start------------->8---
iptables -A wan-f-ssh -p tcp -m conntrack --ctstate ESTABLISHED -m tcp --tcp-flags FIN,ACK FIN,ACK -m recent --set --name ssh --rsource -j LOG --log-prefix "FW+SSH:FIN:"            
iptables -A wan-f-ssh -p tcp -m conntrack --ctstate ESTABLISHED -m tcp --tcp-flags FIN,ACK FIN,ACK -m recent --update --seconds 30 --hitcount 2 --name ssh --rsource -m recent --set --name ssh2  --rsource -j LOG --log-prefix "FW+SSH:FIN#2:"      
iptables -A wan-f-ssh -j ACCEPT                                                                                                                                                                                                                

[...]

iptables -A FORWARD -m recent --update --seconds 60 --name ssh2 --rsource -j DROP
iptables -A FORWARD -p tcp -m tcp --dport 22 -j wan-f-ssh
--8<---------------cut here---------------end--------------->8---

ie. if SSH connection ends, it added to observation (ssh set) then if
second end happens during 30 sec it is added to block (ssh2 set)
I would achieve similar behavior with nftables and I guess that I should
use meters but ... I do not know how.
In some internet sites I found some examples but I do not understand
"why that".
For example:
https://wiki.archlinux.org/title/Nftables#Dynamic_blackhole
--8<---------------cut here---------------start------------->8---
 ct state new tcp dport 443 \
                meter flood size 128000 { ip saddr timeout 10s limit rate over 10/second } \
                add @blackhole { ip saddr timeout 1m }
--8<---------------cut here---------------end--------------->8---

I understand " add @blackhole { ip saddr timeout 1m }" - adds address to
set for 1 min.
but what is
"meter flood size 128000 { ip saddr timeout 10s limit rate over 10/second }"

(I can guess but I cannot see proper doc of this)
Any hint?
KJ

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