Your sketch doesn’t have any # include <> statements for the Blynk libraries, so its impossible for it to compile as it stands.
You’re also using SimpleTimer instead of BlynkTimer, but you don’t have a # include <> statement for that library either…
This line doesn’t belong in this sketch…
and this won’t work with Blynk IoT because it’s a Legacy command…
Even if it did work, or you replaced it with the IoT equivalent (logEvent) then you’d send the same notification once every second while data > 500 and quickly hit the allowed limit for events.
Read this for more info on how to do notifications in Blynk IoT and how to use ‘flag’ variables to avoid unwanted repeat notifications…
Pete.