That’s because your voice command is interpreted as “increase” and not “raise”. The former increase the current state value by 1%. While the latter would send an UP command.
Make sure to use these utterances:
Alexa, fahre die Rollo hoch. (Raise) Alexa, fahre die Rollo runter. (Lower) Alexa, öffne das Rollo. (Open) Alexa, schließe das Rollo. (Close)