Let's consider the piano version of Moldau/Vltava from Smetana, the first two measures for example:
What should be the duration of the blue circled notes, as expressed in units of an eighth note:
Should it be less than an eighth note, or equal to an eighth note?
Is it staccato or something else?
If this is less than an eighth note, then would that mean the right-hand circled notes do not "fill" the rest of the measure? (and if so, why isn't there some sort of silence added to the score?)