If you'd have clicked the link you would have seen that it's a designated
An E9th ChordBoard..... We are talking about CHORDS and KEYS not notes..
So surely the CONVENTIONAL naming of keys should apply.. Who ever heard of A#m or D#7 ?
And If the A# is used because of the tuning and its scalic relationship, then explain just why it's also called A# on this C6 CHORDCHART by the same company..?

The author of those ChordBoards is Rick Kornacker as USA Steel Guitar Forum Member.
I've sent him an E-Mail, I'm interested to see what he has to say about the naming of the chords unconventionally.
I must admit that D#m G#m and A#m seem out of line with present teaching, likewise with some of the straight major
nomenclature, and the sevenths.
Not the norm, and in my opinion not the path to start students upon.