Interpreting the results of offset tracking moudle

hello, offset tracking experts
in the results of offset tracking, i have a Velocity.csv file. It looks like this

it has columns of range_shift and azimuth_shift. i know the absolute values repents the offset distance.But what does the negative and positive values means, or whats their difference?
are the range_shift or azimuth_shift of different image scene(like different path ,frame, orbit direction) comparable?
can experts give me some details about the algorithm of the offset tracking modules.
Thank you for your generous sharing!