Dear @jyoti.grg,
You are in the same situation you were in February (Relation between errors in successive scoring bins).
1-As I already told you, you should not use X-Y-Z USRBIN having 1 single bin in two dimensions, create instead a X-Y-Z USRBIN that while having 1 bin in z can instead create an overview of the the whole plane you are interested into.
2-Since your system has radial symmetry and your interest in a value at a specific radius, you should use a R-PHI-Z USRBIN. If you set R between 32.5 and 32.7 cm with PHI between 0 and 2pi, you will have a nice radial plot at a given z that will use all the particles going through the radii of interest over the whole circumference and not just over a small section of it. If you want to check that the results are radially symmetrical you can set a small number of bins in PHI.
3-Once again, don’t look only at the raw data but have also a look at the plots of the USRBINs.
4-The increase in the dose rate value is due to the fact that your geometry has a radial air gap precisely for that radius, just below the z where you want to score.