Minor additive, can anyone solve this? It's baffling me.

[w122166]

I'm not bothered about the question mark answer, just on how on earth the number "2" in line 6 has been derived? He says "There is a numerical series of 14, 13, 12, which requires that the number shall be one whose integers add up to 2, 11, or 20. But you cannot get the number 12, without pulling the number 2 out of no where?

For the life of me It's as if it has been plucked out of thin air.
The furthest I can progress the numbers to is the image below and then I'm stuck, any ideas guys? much appreciated, Thank you.

[Charlesman]

Is this even numerology?
Or mathmatics? Google search suggests it has something to do with chemistry.

Regardless, the answer is 5.