I can take photos but the second and third tabs are empty; i can't see/set a reference. I tried ensuring the photo had a uk banknote in it (does it matter which?) but it made no difference.
(aside: one would expect a picture taking using camera app to be fairly trivial, but it is actually very challenging on Android, where each vendor implements it with its own little subtleties)
My wallet folds notes but the app is accurate if I try and make them as flat as possible first.