Does Index number start from 0 or 1??

Novice question here, 

Got an IF action in my bot which is looking at an excel row, for the index value I want it to always be a certain column (in this instance it's column G)

My question is, would the index number be 6 (suggesting that column A and the index starts from 0) or would it be 7 (suggesting that column A and the index starts from 1)?

Thanks

Jonny