What are the opimum values of Cl during descent? Statistical Analysis of A320 aircraft shows the Cl values to be as under: cl_value. L is assumed to be 0.5*MaximumLandingWeight of A320 as the Aircraft is about to land.

The Units used are: Flight Level(feet), rho(lb/feet^3, V(feet/s), for the sixth column, 1/2(rho.V^2.S.)
 

The cruise Cl values are as under: 

When compared to cruise the CL during descent is very small. Is this an acceptable result?
I am going to work in SI units for all engineering work, anything else would cause instant insanity on my side. I'll leave the altitude in feet (isn't used) and convert speed from knots to m/s so you can follow the flow easily. Since $C_L$ is unitless it should not matter what units you use in the calculation as long as you are consistent.


Altitude: 34000 [ft] (not used)
$V$ (true air speed): 442 [knots] = 227 [m/s]
S = 112.6 [m2]
$\rho_0$ = 1.225 [kg/m3]
$\frac{\rho}{\rho_0}$=0.322 [-] (from your table)
$\rho$ = $1.225 \cdot 0.322 = 0.394$ [kg/m3]
$\frac{1}{2}\rho V^2 S$ = $\frac{1}{2} 0.394\cdot 227^2 \cdot112.6 = 125\cdot10^4 $[N]
$m$ = MLM = 64500 [kg]
W = $m\cdot g$ = $64500\cdot 9.81$ = $63\cdot10^4$ [N]
$C_L$ = $\frac{W}{\frac{1}{2}\rho V^2 S}$=$\frac{63\cdot 10^4}{125\cdot 10^4}$ = 0.5


I did take full maximum landing mass for this calculation. If you want to apply corrections then note that the $C_L$ value scales linearly with the mass. 

One further note:

I assume your data is derived from ADS-B. ADS-B transmits groundspeed, whilst you should work with true airspeed in these formula's. The difference between them is the tailwind (or headwind) component.