We have produced a guide to finance calculations that is available on Teach Cambridge. This explains the business specific calculations.
In addition, many of the quantitative skills are broader maths skills that are given a business context. For example, students may be asked to calculate averages. This maths skill may be assessed in the GCSE where it will be applied to a business context.
Details of the quantitative skills requirement can be found in appendix 5c of the specification.