1) I redid the calculations using the numbers shown in the table. With more decimal places, it's 1.054 for outdoor and 1.036 for indoor. The actual penalty for outdoor growing, using their own input numbers, is more like 1.7% than 10%. Presenting the results rounded to 1 decimal place is misleading.
2) The only reason indoor comes out ahead at all is that they gave indoor lettuce a 0.18 kg credit for sequestered CO2 and gave the outdoor lettuce no credit. Plants absorb CO2 while growing regardless of whether they are indoor or outdoor. In the case of lettuce, there is no long term sequestration anyway; the plant matter is soon converted back to CO2 when it's metabolized by humans or microbes. Setting both indoor and outdoor sequestration credits to 0, indoor has a CO2 footprint of 1.253, significantly larger than outdoor's 1.054.
The original source for the table is cited as a blog article from the Breakthrough Institute titled "Don't Count Out Vertical Farms." I tried going back to the original source to see if the numbers were misrepresented here, or if they had more justification in the original, but the Breakthrough Institute appears to have removed the article from their site. Existing links to it 404 now.
https://thebreakthrough.org/issues/food/vertical-farms-raise...
It gets worse when you look at the footnotes. They assume that the electricity going to the vertical farm is produced at the Swedish average carbon intensity per kWh. Sweden is far below the OECD average for electrical energy carbon intensity:
http://www.compareyourcountry.org/climate-policies?cr=oecd&l...
Only Switzerland, Sweden, Iceland, and Norway have low enough electrical carbon intensities for vertical farming to have a smaller carbon footprint, even conceding the re-forestation assumption.