In this manuscript we show that the second Feng-Rao number of any
telescopic numerical semigroup agrees with the multiplicity of the semigroup. To
achieve this result we rst study the behavior of Ap ery sets under gluings of nu-
merical semigroups. These results provide a bound for the second Hamming weight
of one-point Algebraic Geometry codes, which improves upon other estimates such
as the Griesmer Order Bound.