AOS compute problem

In function find_aos()
/* coarse time steps */
while ((sat->el < -1.0) && (t <= (start + maxdt)))
{
t -= 0.00035 * (sat->el * ((sat->alt / 8400.0) + 0.46) - 2.0);
predict_calc(sat, qth, t);
}
what does 0.00035、8400.0、0.46、2.0 standfor?