I have seen the duration calculated two different ways.
#1) Seems like 0 starting day: LF-LS or EF-ES : Example Rita book
#2) Seems like 1 starting day: LF-LS + 1 or EF-ES + 1 : Example from PrepCast
How do you know which one you should be using? It makes a difference. If LF=15 and LS =8, then the answer for what is the duration could be either 7 or 8 depending on which calculation used.
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