They might both be due to execute at the same time, and in that case the first one will execute, then te next time that timer.run() is encountered the next one will execute.
This means that the second timed function may execute slightly late, but that wont be a problem.
The problem is when you have say 10 timers that are executed every 500ms, and the 10 timed functions take more than 500ms to execute. Eventually you’ll have such a big backlog of timers in the queue that the device will crash.
These are interval timers, not timeout timers. They keep executing at the same interval so long as timer.run() is being executed.
That doesn’t happen, because the BlynkTimer code is written in a way where millis rollover isn’t a problem.
If you want to know more about timers you should read this…
But none of this is relevant unless you’ve figured-out your non-blocking code for your connection/re-connection routines, and you don’t execute Blynk.run() when Blynk.connected() is true
Pete.