If you want to know something like this then be assertive and speak up and ask the Captain your with...so you are admitting to letting this confuse you on a daily basis whilst working but havent had the sense or assertiveness to ask your colleague who works at your Airline who is sat next to you on the day to explain this to you ?????? You would rather just kinda be not sure but hope or be lucky that you kinda might have done it correctly or hopefully given the right info when asked for the purpose of the weight and balance and take-off performance of the aircraft and then wait until you get home to the safety of your Laptop and then start asking completely random people with names likes BLABLABLA on here who might not actually ever have flown a real aircraft in their life....You Sir are a Smart Man