Anytime you start back after a layoff, the work sets are NEVER calculated. They are titrated up from the warmups. Equations are wrong 90% of the time, because they cannot include all the factors that determine the extrapolated set of 5 TODAY. Start where the workout tells you to start, and go up from there. Your subsequent jumps will be bigger than they were the first time anyway, so if you guessed light by 20 pounds, the error will be made up in at most 2 workouts. But if you start 20 pounds too heavy, you're fucked.