John darksends 2 coins from A to C, gets 8 back as change on address X
a few days later..
John darksends 8 coins from B to D, gets 2 back as change on address Y

Joe darksends 3 coins from E to G, gets 7 back as change on address W
a few days later..
Joe darksends 1 coins from F to H, gets 9 back as change on address Z

Suzie darksends 3 coins from K to Q, gets 7 back as change on address S
a few days later..
Suzie darksends 1 coins from J to R, gets 9 back as change on address T

Now, we make a pool with X+Y+X1+W+Z+W1+S+T+S1.

Pool total output == 60DRK

X+Y+X1 = 10DRK + 10DRK
W+Z+W1 = 10DRK + 10DRK
S+T+S1 = 10DRK + 10DRK

Make sense?