LV wasn't fulfilling the Prophesy?

[gelite67]

No: HPFGUIDX 128173


What the heck did DD mean in OOP when he told Harry that, "He [LV}
set out to kill you when you were still a baby, believing he was
fulfulling the terms of the prophecy.  He discovered, to his cost,that 
he was mistaken, when the curse intended to kill you backfired." 

LV was mistaken because the curse backfired?  The curse backfired 
because he was not fulfilling the terms of the prophesy?  

I understand that LV didn't hear all of the prophesy, but I don't 
understand how he was "mistaken" -- didn't he fulfull the first part
of the prophesy re marking Harry as his equal (assuming the marking is
the attempt to kill Harry)?

If it was a "mistake" to attempt to hear Harry without hearing the
full prophesy, the old Voldy has made several mistakes since SS.