Hi!
I got confused today... I'm gonna study in Shaolin Kung Fu School in China and with the invitation letter from that school I applied for F type visa for 6 months in chinese embassy in Poland. On the pick up form I got after my documents were received, it is written that I will get 2 visas for 90 days...

What is the difference between 1 F visa for 180days and 2 visas for 90 days??
Do I have to leave China after the 1st visa is expired in order to activate the 2nd visa??? Or how does it work?

Thanks!