In “Numbers and Variables”, before “and a rule that allows Contractors to transfer a numeric value only allows them to transfer that value from themselves to another Contractor (of their choice unless otherwise stated)”, add:-

a Contractor can spend only their own values,

Replace “A Contractor’s Funds divided by their investment is their Return on Investment, or ROI.” with:-

A Contractor’s Funds divided by their Investment is their Return on Investment, or ROI - unless their Investment is zero, in which case their ROI is zero.