I don't understand how multiple @ symbols work in the DNS settings
Absolutely like any other kind of resource record, there is nothing special about this, it is a shortcut to the zone itself.
For the zone
@ IN MX 10 mx1.example.com.
@ IN MX 20 mx2.example.com.
@ IN A 192.0.2.137
@ IN A 192.0.2.201
@ IN AAAA 2001:DB8::ABCD
@ IN AAAA 2001:DB8::1
is exactly the same as:
example.com. IN MX 10 mx1.example.com.
example.com. IN MX 20 mx2.example.com.
example.com. IN A 192.0.2.137
example.com. IN A 192.0.2.201
example.com. IN AAAA 2001:DB8::ABCD
example.com. IN AAAA 2001:DB8::1
So for the explanation of what happens when multiple records for same label, it is exactly the same: resource records are sets (and not lists, as there is no order), so each relevant record is returned for a given query on a type.
@ is just a shortcut when writing the zonefile. It has no impact on how the DNS messages are exchanged, and does not appear in packets.
And to go back to your question, each element of the set is independant of the other, so you change change one without impact to the other (they will still be replied together for the relevant query).
Special rules apply of course when you change or add a new resource type such as a
CNAME that has specific constraints.
You can change the IP address of your
@ A record it will impact only resolutions of your zone name as label (because
@ is your zone name), it will not impact resolution of
pairings label or other ones (except if they are
CNAME records towards the zone name of course, in which case the change in the
A record will apply to all of them, as it is the exact purpose of a