I applied while living in Calgary maybe 4 years ago..

By now I did the online assessment 3 times, when I first applied I did not get any response back only saw wait for in person assessment.
During the time I moved to SK, after emailing them, they did the move from Edmonton to Winnipeg. In the mean time their website also changed.
The second time I did the assessment I got the emailed for an in person assessment (probably 2-3 years in), but I could not sign up before it filled up (sometime March this year)
I just did the third assessment a couple days ago and I got an email about the in-person assessment sign up (testing in Nov)
The email says
"Please note that this assessment is ONLY for a career as a Flight Service Specialist. If you are interested in a career as an Air Traffic Controller, please do not sign up for the testing session."
I am interested in ATC more so should I leave it )= , will there be a chance to switch/transfer over down the line if I do it since it looks like they are hiring/training for FSS this round or just go do it anyways and see what happens.
Also about the 18 months timeline, how does that work? From last activity? or first signing up? confusing and long wait times with this ..