Shows up and then down arrow. In the example four notes are played upward
within the time value of the eighth note chord, then four notes are played downward
within the time value of the next eighth note chord. Speed wise can vary but usually it is quite quick as the four notes are left to ring out to fill up the time value of the indicated chord.
Mainly you don't have time for your hand to bounce up and down when playing the notes. So for practice on having a steady hand on the up arrow notes first place your four fingers (p-i-m-a) down on the strings, then peal them off upward. That's your
ideal hand movement on the downward arrow notes (albeit it's more difficult to do).