I didn't know how to contact the ATTinyCore developer, so I wrote here. Right now, after your message, a brilliant idea came to me - to read the documentation for ATTinyCore. 
This is amazing - it turns out that you can download programs to ATtiny via the serial port! I discovered a lot of new things for myself. Thank you very much! But is it possible to correct the fuses setting to remove the warning?
I apologize for not starting to read the documentation right away and just asked an extra question. I thought there would be only a superficial description.