Palo Alto Networks Inc (NASDAQ: PANW) is trading down in extended hours even though its reported market-beating results for its fiscal second quarter.Why is Palo Alto Networks stock down in after-hours?Copy link to sectionThe stock is being punished primarily on the muted guidance. Palo Alto Networks now forecasts total billings to fall between $2.30 billion and$2.35 billion in Q3. Analysts, in comparison, were at billion. Still, Nikesh Arora – the chief executive of Palo Alto Networks said in a press rele ...