In this example (first cube) only two of four misplaced facelets match the setup for Sequence 3C-E1 (second cube), the blue facelets on the front and back faces should be red. Press Play on the first cube to see that the two yellow misplaced facelets get fixed and the two blue ones remain misplaced. The red misplaced facelets are not part of the setup and can be ignored.

Here is an example for Sequence 3C-E3. On the first cube, the two yellow misplaced facelets on the left & right faces match the setup (second cube) but the red ones on the front face do not. Press Play to fix the two yellow misplaced facelets, the red ones remain misplaced. The blue misplaced facelets on the bottom face are not part of the setup and can be ignored.

Here is an example for Sequence 3C-E4. The two blue facelets match the setup but the yelow & red ones do not. Press Play to fix the two blue misplaced facelets, the other two remain misplaced.

The next step is to look at what happens if only one of the four misplaced facelets can be matched.