CB1 is an instrument of calculation.
CB2 is a planning tool. It helps you to decide to expand or shrink your portfolio of products. It contains multiple CB1 sheets: one sheet for each SKU.
Screen shot of CB2 CONTRIBUTION ANALYSIS sheet: this company has a portfolio of 50 SKUs. Line 31 shows the margin % of each SKU. Line 43 shows importance of the SKU for the company: the higher the contribution, the more important.