  Considered contribution to the phase of the atom interferometer caused by the
gravity field of the massive proof mass. Demonstrated the method of finding the
extrema of this contribution for 100kg Tungsten proof mass of the specific
shape and specific parameters of $^{133}Cs$ atom interferometers. Calculated
variations of the double difference response under the small deviations of
atomic and proof mass variables. The choice of the extremal values of the
atomic variables allows one to release requirements for atom positioning on 2
orders of magnitude.
