Correct. Keep in mind that Sharp means half-step up and Flat means half-step down. if you need need to tune your low E string to Eb, for example, it makes no difference if your tuner says D# or Eb. The two are the same note, and they always will be. In your case, you want to find a scale in the key of A# (or Bb), so you can just go ahead and click on the A#/Bb button. It's really just a matter of opinions, really. Some prefer A#, others prefer Bb, but it's still the same note.

Hope this helps clear up some of the confusion.