Difficulty reading alignment violations

[officialtony]

I did a scrimmage last night and had a very difficult time reading overlaps. Is there someplace where I can get good descriptive advice on how to read back-row-setters positioning clues or something that will help me learn to interpret that when the receiving team is set up a certain way, I know it is a back row setter and where they all should be aligned?
I am only recently doing the level where this appears to be ( or will be ) commonplace, and I want to be sure I am correct in my calls/no-calls.

Thanks in advance.