same case
I am also in same situation. I applied on 24 Feb. and few days back (on 17th Apr.) I got "notice of action" from INS. and on that notice date is 12 Apr and received date is 24 Feb. I was also very confused. And I searched a lot on web and found that rule regarding which date to consider as the start of 90days differs from state to state. In some state they consider notice date and in some they consider received date. So, I can;t say anything abt u as u didn't mention ur state.
The best thing is go to ur local INS and ask them. If they consider notice date (that means 12 Apr), go to ur bank and ask for your "OPT fee" check (the check u posted with ur application to INS). On the back of that check you can see ur SRC# and the date it got cleared. I am guessing that it will be arround 17 Feb (as ur received date is 10 feb). Take only the copy of that check (don't take "notice of action") with other required doc to INS.
What i wanna say is that they consider the copy of that cleared check and will consider that date (on ur check, the date check got cleared) as the 1st day.
I hope this will help you. Please post me any developments as I am also in the same situation . and please tell me ,which state are you in.