I did week 5 day 3 today. It was tough. I stuck to the 30-45seconds between the sets until the 8th level when I had to do 40 pushups: a swift 25 followed by a slow struggle to 40 by which time I was sweating. Then I did heel/toe walks for strengthening my compartment muscles.
In total, I did 18+18+16+16+14+14+12+40 = 148 pushups. Tomorrow, maybe a recovery run or a 10K. We will see.