Forget the legend on the AA timetable: it is wrong.

AA labels the 76s as follows:
762: 767-200 and 767-200ER
763: 767-300ER

As such, there is no way of telling from the schedule when you get the -200 (not as confy) vs. the -200ER. Some guidelines will help, such as the one that all 762s in and out of ORD, MIA or DFW are -200ERs (i.e. continuations of International flights). However, when it comes to JFK (where there are 12 daily 762 transcons), knowing which is of the crammed variety is not easy.
The only way is to ask a res agent to look at a seat map for first and determine if row 4 exists (bad).