re-entry permit date / citizenship

[ICETR]

i reaaly appreciate if someone can help me to understand wich date should I consider to count 5 years that are nedeed for citizinship ? Re-entry permit expire date or d my return date in USA ? I mean I got my reentry permit for two years but I came back in USA before my rientry permit expire date.

re-entry permit expire date. 07/15/2016

i came back in USA 01/10/2016

Thank you in advance for help.