The
aircraft envelope starts from the origin so v = 0 and n = 0, but the gust
envelope starts at v = 0 and n = 1 because we have n = 1 in straight and level
flight. The gust envelope is superimposed over the aircraft envelope to give
reference points. Vb, the design gust load decreases
linearly from MSL to altitude.
If L = 0 then n = 0. Zero divided by anything is zero. You will be weightless,
like in a bunt.