I have a cyclone 5 gx starter kit where i am trying to create a hardware that counts number of pulses generated by a source? according to logic count should increase every negative edge by one but actually it increases by 7 or 8.

Hi i got the culprit as you said, previously i was testing the output of the speed encoder that was clean but missed to check the output of logic level shifting circuit. i used it as the encoder works for 5v and board accepts only 3.3v on GPIO. after the logic-level shifting circuit because of switching ringings is present. It that stays for a time of 4us before signal stabilizes. I will add a de-bounce circuit to clean that up.