Alerting Engine and Rules Guide - What VALUE are evaluated?

using Grafana 6.6.2,
i’m receiving emails for NO data Alert,
but not when “condition” are met.
i read this documentation page https://grafana.com/docs/grafana/latest/alerting/rules/
and to make a try i put a rule to obtain an email alert when the max value of the A query is above 1 : ever.

This is the A query

image

this query returns two values : a timestamp and a number. What number is considered in the MAX condition?

as a human, i think the value are evaluated,
but as a query result,
how grafana can choose?