Can someone help me to calculate the approx refrigerent charge ( kg) in a chiller

I have a Mercury Climate chiller that has four danfoss SZ185-4 Maneurop compressors running on R407C. Each compressor is rated at 52kW cooling capacity. Evap temp is 7.2 deg C, condensing temp is 54.4 deg C.
The suction press is 4 bar and the high press set at 20 bar.
Should the charge be around 13kg per compressor. Two circuits of two compressors eqaulling 26kg each?
Thanks