Multithreading mode

Hi! Tell please is there possibility to make calculations using flair in multithreading mode ?

Yes, look the spawn field in the Run tab.
Is not real multi threading mode in a single run, but poor man parallelization, launching in parallel many jobs with different random number sequence. In the end it will sum up all results like being one.

What means the number I should insert there ?

Indeed is the number of cores/threads you want to run in parallel.