I'm playing Schubert's 3rd impromptu, op. 90 D899. There is a circled number precisely under each trill, shown below, and I don't know how to interpret them.
I read here that they might indicate a change in the hand's position, but then
- I don't see why the circle notation would be restricted to trills (as the left hand has to do other brusque shifts) and, more importantly,
- it doesn't explain the circled 7 and 8!
Certainly the circled 1, 2 and 5 match the fingering of their respective notes, but how should I interpret the other two numbers? I don't think that they mean intervals as they seem too vague a notation for that purpose and they don't sound right to me.
Any clue on how to play these trills?