Bar execution time implementation

[wombatinua]

Version: 2.8.6

When I measure my app's execution time with Debugger::timer(); or the following code

$start = $_SERVER['REQUEST_TIME_FLOAT'] ?? microtime(true);
// ...
$end = round(((microtime(true) - $start) * 1000), 2);

I always get execution 1.5 - 2 times (roughly) smaller than shown in Tracy Bar. Why is it so? Does Tracy Bar takes into account network delivery time or something?

Is it possible to access Tracy Bar execution time within my code (if my implementation is not right)?

This is not a bug, but a thing which I appreciate to be explained. Thanks in advance.