Judging by the formula, I think 1.31 would be the quantity of the given lamp you used in the formula needed to get to 30 LSI. Basically, one lamp with 2835 lux wouldn't be enough to reach 30 LSI. With that lamp, you're looking at 22.86 LSI (2835 lux divided by 124 inches squared).
I hope I didn't make you more confused! LOL