I a Coda table we work differently compared to a spreadsheet, the year as number in a column, the interest as a number in a column, the amount in a column and the outcome in a column. Since we execute the calculation per row, we simple add a new row to see the results coming on that same row. This logic alignes well with the remarks of
Also, Coda - as well as other relational oriented data tools - favorites a row-based approach rather that a column-oriented. Meaning that it is usually easier add a row than a column and if you follow this principle
Average per month you’ll take full advantage of the tool.