Problem to read_data file

Hello sir,
I have a geometry of particles as a disc in two dimensions that I implemented according to the documentation I read, is this geometry is ok for particles as disc calculation?
My second question is about the value of 0.333333 in the read_data file from the below code that I generated?

LAMMPS data file via write_data, version 17 Feb 2022, timestep = 1000
100 atoms
1 atom types
0 11.180339887498949 xlo xhi
0 11.180339887498949 ylo yhi
-0.05590169943749475 0.05590169943749475 zlo zhi
Atoms # sphere
1 1 0.9 0.33333333333333337 0 0 0 0 0 0
2 1 0.9 0.33333333333333337 1.118033988749895 0 0 0 0 0
3 1 0.9 0.33333333333333337 2.23606797749979 0 0 0 0 0
4 1 0.9 0.33333333333333337 3.3541019662496847 0 0 0 0 0
5 1 0.9 0.33333333333333337 4.47213595499958 0 0 0 0 0
.
.
please clear my confusion about how this value is calculated and is the density or mass of the disc?

clear
units lj
dimension 2
boundary p p p
atom_style sphere
lattice sq 0.8
region box block 0 10 0 10 -0.05 0.05
create_box 1 box
create_atoms 1 region box
group mobile type 1
set group mobile diameter 0.9
set group mobile density/disc 0.20
fix 1 all nve/sphere disc
fix 2 all enforce2d
timestep 0.002
dump DUMP all custom 50 dump.lammpstrj id type x y z
run 10
write_data data.in

If the explanation for a per-atom property is not given in the documentation of the read_data command — LAMMPS documentation
then you can usually look it up in the documentation for the set command — LAMMPS documentation