As argv0 said, only the first
matching event in a file will trigger. If you have two events definitions that are mutually exclusive then they will both trigger when expected, but if you have two event definitions that can both match a single line of text then only the first one will trigger.
A clear example of this is:
on *:TEXT:*:*:echo -a This event will trigger for all messages
on *:TEXT:anything:*:echo -a This event will never trigger at all