How it works
One deposit compounds annually at the rate prevailing when the certificate is bought, and the whole amount is paid at maturity. The rate is locked for the term, which is a real advantage over a bank deposit whose rate can be reset when it renews.
The table shows interest year by year rather than only the total, because that is the figure your tax return needs. Interest accrues and is taxable each year even though nothing reaches you until the end.
More detail
There is a useful consequence of that. The interest reinvested in years one to four counts as a fresh Section 80C investment in each of those years, so an NSC bought once quietly contributes to four subsequent years' deduction limits. Only the fifth year's interest has no such offset.
A ₹1,00,000 certificate at the current 7.7% matures at ₹1,44,903 — the same figure published maturity tables quote, which is the check that the annual compounding here is the convention the scheme actually uses.
For the scheme designed to double your money instead, see the Kisan Vikas Patra calculator.
To compare against a bank deposit, use the fixed deposit calculator.
To see what the annual interest costs you in tax, try the income tax calculator.