>>Also this could be a good place to ask: is each volume calculated taking ALL SETS/REPS on the cycle? would I have less preparation if I don't do all warming up sets? 
Lets take squats. Then for each week the number of reps and volume are calculated and one can aggregate that into monthly length or length of the (prep./comp.) cycle. Since Sheiko starts programs at 50% (given comp. squat) everything that is below that is not counted. You should still do a thorough warm-up and proper series until 50%. Search forum for "warm up" if you want to know more about this.
Please be aware that Boris likes to write variations of a given exercise and adjust percentages according to the comp. lift.