Holy shit, a spider!
In this exercise you play the 1-2-3-4 pattern on each string. What makes it difficult is that when you change strings the finger should be placed on the string while the others are still resting in a row on the previous string! This exercise should be played very slowly to train your fingers to make tiny movements on the fretboard which really pays off at higher speeds.
Let's say you're playing the regular spider (playing the 1-2-3-4 pattern on each string), these photos show how your fretting hand should look: