Grasp pwd lenght from .cap

[Algreen]

Forgive me if question out of context.
Is it possible to know pwd lenght from .cap file?
I got following Wireshark eapol filtered outputs:
2th handshake: WPA Key Length: 22
3th handshake: WPA Key Length: 80

   
Are these books usefull to learn such procedures?

• BackTrack 5 Wireless Penetration Testing Beginner's Guide
  
• BackTrack-5-Cookbook
  

Thanks in advance
Al