(budget layout) How-the-Numbers-Work.md: annual list, rest, vs budget, saved by retirement
(v2 savings, cost types) How-the-Numbers-Work.md: contributions and balances over time
(retire ages) How-the-Numbers-Work.md: income and spending with separate ages
(window end) How-the-Numbers-Work.md: document plan.last_month
(wiki docs) How-the-Numbers-Work.md: documentation page