Please excuse my ignorance on this, but when determining the baseline to compare, I understand that it depends on the substantial completion date of the plumbing system and if before 1993, then use 160% and if after, use 120%. So if my building was designed and built in 2000, then I use 120%. Problem is, what does that mean? Where do I use 120%. What is that used as my mutiplier against what? Guide book says "of the water use that would result if all fixtures met the codes cited (in UPC/IPC)." Can someone explain that to me in english as to what that means?