A few sentences giving an overview of the spreadsheet.
This is fairly straightforward. Just follow the instructions. The labels (headings) can be adjusted using the formatting toolbar. Select appropriate fonts (Arial, in this case), point sizes and bold as needed. About the only thing not explained is how to get the horizontal lines above and below the totals.
After creating the SUM formula in cell C8, go to Format > Cells… > Border (the arrow means the selection from the sub-menu) and select the line style then the position. You get a preview in the large centre box labeled "text". You can make up any numbers you like for the "raw data", but try to be realistic. We're not asking you to expose your personal worth. J Notice that a Deficit, i.e. a negative amount, should be formatted with brackets around an unsigned number.
The formula for the cosine function, =COS(A3*PI()/180), should be constructed using the "point-and-click" technique, as should all formulas in the future. Why? It's generally quicker and more accurate, especially when the formulas get complex.