Now that I am reclassifying, how can I determine my second phase or duty station from my class code on my ERB?

Look in ATRRS course catalog.

What does AEA/DT means? mine says: M / 201909

I just completed the 68C on July 11th. My phase 2 site was at Fort Bliss. There are 10 classes a year and 5 different phase 2 sites. Your phase 2 site is subject to change, even as prior service. We had a bunch mildly upset about the change.
The order of phase 2 sites go as follows,
01-Fort Lewis-McCord
02-Fort Gordon
03-Fort Bliss
04-Walter Reed
05-Fort Sam Houston
Repeat in same order.
Each class is 5 weeks apart and 01 begins at the very beginning of the fiscal year.

I first arrived in Sam Houston at the end of May and was scheduled as the 18-007 heading to Fort Gordon. Fort Gordon did not have enough available slots for our class size(30 slots to 52 students) and so I was held over and sent to Fort Bliss as class 18-008. Don’t become too focused on where you’re going, focus on finishing. The course is not difficult. But it’s very easy to burn out, lose hope, stress and overwhelm yourself. We started with 52 students in phase 1, and ended with 38. Some hold overs from the class before were then sent to Gordon and it gets really complicated as far as number goes. Just know the new class gained another 17 and began phase 2 with 55, and ended with 30 and a 100% NCLEX pass rate. It’s certainly doable, just stay proactive and motivated.