For 2020, the amount that you should enter is for the Investment Standard Calculation, line 12. Line 15 is for the penalty, if any, which isn't what you need. 16 is a type-o, as you pointed out.
Here is a TurboTax article with some information about designated Qualified Opportunity Zones and how you can get a potential tax savings.
There are designated Qualified Opportunity Zones located in all 50 States, the District of Columbia, and five United States territories. Over the past three years, Qualified Opportunity funds have raised $75 billion, which has been a direct investment into the most underserved areas in our country.
An Opportunity Zone Fund investment provides potential tax savings in three ways:
#1: Tax Deferral through 2026. A taxpayer may defer the tax on a capital gain when investing in a Qualified Opportunity Fund if they comply with the investing timeframe restrictions. The taxpayer has 180 days to invest but Notice 2020-39 extended the investment deadline to Dec. 31, 2020 if the 180th day to invest would have fallen on or after April 1, 2020, and before Dec. 31, 2020.
#2: Step up in tax basis of deferred gains. The “5-year, 10% basis increase” is still available for taxpayers through Dec. 31, 2021.
Example: In July 2021, a taxpayer sells a zero-basis business for $5 million, which triggers a $5 million capital gain. The taxpayer invests the entire amount in a Qualified Opportunity Zone Fund within the timeframe restrictions, resulting in no tax on the sale proceeds in 2021. On Nov. 1, 2026, the taxpayer receives a 10% adjustment to their cost basis in the Qualified Opportunity Zone investment amounting to $500,000. On Dec. 31, 2026, the taxpayer must recognize the deferred gain on the sale of the investment, and their cost basis for determining the total gain is $500,000. Assuming the overall value of the Quality Opportunity Zone investment has not decreased, then the taxpayer will pay the capital gain on $4.5 million ($5 million 2021 gain, reduced by the 5-year 10% basis adjustment of $500,000) and the taxpayer must reflect that gain on their 2026 federal income tax return to be filed in 2027.
#3: No tax on appreciation. If a taxpayer stays in the Qualified Opportunity Fund for at least 10 years the cost basis of the property will equal the fair market value on the date of sale/exchange.
@julesstcroix03
