I have seen some sites where the referal leves are organized in different ways
something like 10,8,5,2,2,2... (just an example)

can anyone explain me what does it mean?

if i'm not mistaken, that's the % of commision you earn from your referrals

for example, 10,8,5,2,2,2 would mean,
you get 10% of your first tier referrals' earnings
you get 8% of your second tier referrals' earnings
you get 5% of your third tier referrals' earnings
you get 2% of your fourth tier referrals' earnings

and so on

am i right?

Yes. You are correct.

oh I see
thank you very much for your help