Xdebug profiling shows different execution time than actual one

Question

I am profiling my website and when I use Xdebug profile on one of my pages I got results that states:

1977 different functions called in 3900 milliseconds (1 runs, 1977 shown)

But the actual execution time measured at top and bottom of index.php file states:

20 seconds

Where I am losing so much seconds ?

How to check what takes that time ?

Answer 1

I found out that webpage I was profiling got a redirect. So the profiler showed time for the profiling page but my measurements in index.php showed time after redirect.