The theory of different outcomes as time changes and progress… in a linear form. This then allows someone to adjust the percentage as they go along. However not always is this need to write a formula. You can have and or similar to greater then or equal to which can also be used in this aspect.
They at a stage that presents a pretty complicated problems more commonly become known as algorithms when they are proofed in general theory applied to. This is either the theory applied or it does not. This is not due in o the equation being wrong but it could need to tweaked or adjusted.