What is the output of Software Serial .read() function
It is just like https://www.arduino.cc/en/Serial/Read : 

The monitor.find("OK"); already consumed the 'O' and the 'K' bytes, (see https://www.arduino.cc/en/Serial/Find ) then there were two bytes .available(), a 13=CarriageReturn and a 10=LineFeed, both returned by successive monitor.read()s, then zero more bytes in monitor.available().