Calculating work order start date for variable lead time item

Q1. I am struggling to understand how to apply the formula for calculating the number of days to back schedule to determine the work order start date. Doc ID 626117.1 displays a formula that sums upto 4 components (lead time in days + lead time in hours converted to days + queue time in days + set up time in days) depending on how PO #3 in the defaults tab of P48013 and R30822A and also the hours per day in the manufacturing constants compared with the totals hours from the work centre(s). Doc ID 881632.1 displays a similar formula of lead time in days + queue time in days + set up time in days but doesn't seem to mention that this is modified under the conditions mentioned in 626117.1 Which document is right?