The the giant set's just wanted to know if u wanted a set of each different technique or break them up each set?
You do exactly what it says, in the order it says.
So for example: with the flat DB flye you'd do 8 reps with a 2-second contraction and then 8 reps on a decline with a 5-second negative and then 8 partial rep presses (24 reps total), then go right into pec-deck 10 reps and one drop set for another 10 reps (20 reps total), then go right to wide stance push-ups to failure. Then rest 2-3 minutes before doing another 1-2 sets. Rest 2-3 minutes after the last set and then attack Giant Set #2.