This is starting to sound like a bug in the PF data file, and should be reported to LW.
Using TWF with unarmed strikes was answered in an Paizo FAQ in 2013:
https://paizo.com/paizo/faq/v5748nruor1fm#v5748eaic9qie
Unarmed Strike: Can I use two-weapon fighting to make two unarmed strikes in one round?
Yes.
I image the actual number of attacks a character would receive would depend on it's BAB and other feats (ITWF, GTWF, etc.). But at the base line with a 1st level character who selected TWF (without Improved Unarmed Strike), they should have 2 unarmed strikes, though those strikes would be nonlethal and provoke attacks of opportunity. And those attacks would be at -2 each.