[nftables] icmp type rate limiting - cumulative for the daddr or selectively per saddr?

[ѽ҉ᶬḳ℠ <vtol@xxxxxxx>]

https://wiki.nftables.org/wiki-nftables/index.php/Rate_limiting_matchings 
is not clear whether the 'limit rate' stanza applies as:

* cummulutive limit (from any/all saddr) for the daddr within the given 
period

or

* assumes/implies limit selectively for each saddr within the given period

If it is a cummulutive limit how to go about a limit per saddr? For example:

icmpv6 type 128 ip6 saddr limit rate over 15/second burst 3 packets drop

or

icmpv6 type 128 { ip6 saddr limit rate over 15/second burst 3 packets } drop

producing:

Error: syntax error, unexpected saddr, expecting comma or '}'